Information processing device and information processing method

ABSTRACT

Generation and management of a communication path between a plurality of information processing devices are properly performed. 
     An information processing device is an information processing device equipped with a communication unit and a control unit. The communication unit exchanges a signal for generation or updating of a multi-hop communication path using wireless communication with another information processing device. In addition, the control unit performs control such that, when there is path information regarding a communication path to another information processing device in a case in which the signal for generation or updating of a multi-hop communication path is transmitted to the other information processing device, the signal is transmitted to the other information processing device in unicast, and the signal is transmitted in broadcast.

TECHNICAL FIELD

The present technology relates to an information processing device.Particularly, the technology relates to an information processing deviceand an information processing method for dealing with informationregarding wireless communication.

BACKGROUND ART

In the related art, there are wireless communication technologies forexchanging various kinds of data using wireless communication. Forexample, a communication method for making an autonomous connection witha nearby information processing device (for example, ad hoccommunication or an ad hoc network) has been proposed (for example, seePatent Literature 1).

CITATION LIST Non-Patent Literature

-   Patent Literature 1: JP 2009-239385A

SUMMARY OF INVENTION Technical Problem

According to the technology of the related art mentioned above, variouskinds of data can be exchanged between two information processingdevices using wireless communication, without connection on a wirednetwork. In addition, on such a network, each information processingdevice can perform communication with a nearby information processingdevice, without depending on a master station such as a control device.Furthermore, on an ad hoc network, when a new information processingdevice appears nearby, this new information processing device can alsofreely participate in the network. Thus, network coverage can be widenedin accordance with an increase of nearby information processing devices.

In addition, on top of such an autonomous connection with a nearbyinformation processing device, each information processing device canalso transfer information to be exchanged with another informationprocessing device in a bucket brigade manner (which is so-calledmulti-hop relay). In addition, a network using multi-hop is generallyknown as a mesh network.

As described above, on an ad hoc network or a mesh network, it ispossible to freely communicate with nearby information processingdevices. In addition, the network can be expanded while connections withinformation processing devices around are being made. In this case, itis important to appropriately generate and manage a communication pathbetween the plurality of information processing devices.

The present technology takes the above circumstances into consideration,and aims to properly generate and manage a communication path between aplurality of information processing devices.

Solution to Problem

The present technology has been made in order to solve theabove-mentioned issues. According to a first aspect of the presenttechnology, there is provided an information processing device, aninformation processing method, and a program for causing a computer toexecute the method, the information processing device including acommunication unit configured to perform exchange of a signal forgeneration or updating of a multi-hop communication path using wirelesscommunication with another information processing device; and a controlunit configured to perform control in a manner that, when there is pathinformation regarding a communication path to another informationprocessing device in a case in which the signal is transmitted to theother information processing device, the signal is transmitted to theother information processing device in unicast, and the signal istransmitted in broadcast. Accordingly, the effect that the signal istransmitted in unicast when there is the path information regarding thecommunication path to the other information processing device in thecase in which the signal is transmitted to the other informationprocessing device, and the signal is transmitted in broadcast isexhibited.

According to the first aspect, the control unit may transmit the signalin broadcast when there is no path information regarding thecommunication path to the other information processing device.Accordingly, the effect that the signal is transmitted in broadcast whenthere is no path information regarding the communication path to theother information processing device is exhibited.

According to the first aspect, when a communication path which has beenproactively generated is set and a signal for updating the communicationpath is transmitted, the control unit may transmit the signal in unicastto an information processing device serving as a next destinationspecified with path information regarding the communication path andtransmit the signal in broadcast. Accordingly, the effect that thesignal is transmitted in unicast to a next destination informationprocessing device specified with the path information regarding thecommunication path when the communication path which has beenproactively generated is set and the signal for updating thecommunication path is transmitted, and the signal is transmitted inbroadcast is exhibited.

According to the first aspect, when a path request signal of which adestination is the information processing device has been received asthe signal, the control unit may cause a path reply signal correspondingto the path request signal to be transmitted in the unicast and thebroadcast to a transmission source station which is an informationprocessing device which has transmitted the path request signal first ata timing at which a predetermined period of time elapses from receptionof the path request signal. Accordingly, the effect that, when the pathrequest signal of which the destination is the information processingdevice has been received, the path reply signal corresponding to thepath request signal is transmitted in unicast and broadcast to thetransmission source station of the path request signal at the timing atwhich the predetermined period of time elapses from reception of thepath request signal, is exhibited.

Advantageous Effects of Invention

According to the present technology the excellent effect ofappropriately generating and managing communication paths between aplurality of information processing devices can be exhibited. It shouldbe noted that the effect described here is not necessarily limitative,and any effect described in the present disclosure may be exhibited.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram showing a system configuration example of acommunication system 200 according to a first embodiment of the presenttechnology.

FIG. 2 is a block diagram showing an internal configuration example ofan information processing device 100 according to the first embodimentof the present technology.

FIG. 3 is a diagram showing an example of a signal format of a packetexchanged between information processing devices which constitute thecommunication system 200 according to the first embodiment of thepresent technology.

FIG. 4 is a diagram showing examples of signal formats of a managementpacket exchanged between the information processing devices whichconstitute the communication system 200 according to the firstembodiment of the present technology.

FIG. 5 is a diagram showing an example of the content of the signalformat of the management packet exchanged between the informationprocessing devices which constitute the communication system 200according to the first embodiment of the present technology.

FIG. 6 is a diagram showing an example of the content of the signalformat of the management packet exchanged between the informationprocessing devices which constitute the communication system 200according to the first embodiment of the present technology.

FIG. 7 is a diagram showing an example of the content of the signalformat of the management packet exchanged between the informationprocessing devices which constitute the communication system 200according to the first embodiment of the present technology.

FIG. 8 is a diagram schematically showing an example of a mesh pathtable (mesh path table 340) retained by each of information processingdevices which constitute the communication system 200 according to thefirst embodiment of the present technology.

FIG. 9 is a diagram showing a generation example of a reactive mesh pathretained by each of the information processing devices which constitutethe communication system 200 according to the first embodiment of thepresent technology.

FIG. 10 is a diagram showing a generation example of a reactive meshpath retained by each of the information processing devices whichconstitute the communication system 200 according to the firstembodiment of the present technology.

FIG. 11 is a diagram showing an example of generation of a proactivemesh path by each of the information processing devices which constitutethe communication system 200 according to the first embodiment of thepresent technology.

FIG. 12 is a diagram showing an example of generation of a proactivemesh path by each of the information processing devices which constitutethe communication system 200 according to the first embodiment of thepresent technology.

FIG. 13 is a diagram showing an example of generation of a proactivemesh path by each of the information processing devices which constitutethe communication system 200 according to the first embodiment of thepresent technology.

FIG. 14 is a diagram showing a generation example of a reactive meshpath retained by each of the information processing devices whichconstitute the communication system 200 according to the firstembodiment of the present technology.

FIG. 15 is a diagram showing a generation example of a reactive meshpath retained by each of the information processing devices whichconstitute the communication system 200 according to the firstembodiment of the present technology.

FIG. 16 is a diagram showing a generation example of a reactive meshpath retained by each of the information processing devices whichconstitute the communication system 200 according to the firstembodiment of the present technology.

FIG. 17 is a diagram showing an example of generation of a proactivemesh path by each of the information processing devices which constitutethe communication system 200 according to the first embodiment of thepresent technology.

FIG. 18 is a diagram showing an example of generation of a proactivemesh path by each of the information processing devices which constitutethe communication system 200 according to the first embodiment of thepresent technology.

FIG. 19 is a diagram showing a case in which a valid mesh path is set inthe communication system 200 according to the first embodiment of thepresent technology.

FIG. 20 is a diagram schematically showing the flow of data when theinformation processing device 100 according to the first embodiment ofthe present technology updates the valid mesh path.

FIG. 21 is a diagram schematically showing an example of a mesh pathtable (mesh path table 350) retained by each of the informationprocessing devices which constitute the communication system 200according to the first embodiment of the present technology.

FIG. 22 is a diagram schematically showing the example of the mesh pathtable (mesh path table 350) retained by each of the informationprocessing devices which constitute the communication system 200according to the first embodiment of the present technology.

FIG. 23 is diagram showing an example of updating of the mesh path table350 retained by the information processing device 100 according to thefirst embodiment of the present technology.

FIG. 24 is a flowchart showing an example of the process procedure ofsignal processing by the information processing device 100 according tothe first embodiment of the present technology.

FIG. 25 is diagram showing an example of updating of the mesh path table350 retained by the information processing device 100 according to thefirst embodiment of the present technology.

FIG. 26 is diagram showing an example of updating of the mesh path table350 retained by the information processing device 100 according to thefirst embodiment of the present technology.

FIG. 27 is a flowchart showing an example of the process procedure ofsignal processing by the information processing device 100 according tothe first embodiment of the present technology.

FIG. 28 is a flowchart showing an example of the process procedure ofsignal processing by the information processing device 100 according tothe first embodiment of the present technology.

FIG. 29 is a diagram showing a threshold value used when the informationprocessing device 100 according to the first embodiment of the presenttechnology adjusts a transmission trigger of a PREQ.

FIG. 30 is diagram showing an example of updating of the mesh path table350 retained by the information processing device 100 according to thefirst embodiment of the present technology.

FIG. 31 is a flowchart showing an example of the process procedure ofsignal processing by the information processing device 100 according tothe first embodiment of the present technology.

FIG. 32 is a diagram showing an example of transmission of PREQ by eachof the information processing devices which constitute the communicationsystem 200 according to a second embodiment of the present technology.

FIG. 33 is a diagram showing an example of transmission of PREQ by eachof the information processing devices which constitute the communicationsystem 200 according to a second embodiment of the present technology.

FIG. 34 is a flowchart showing the process procedure of signalprocessing by the information processing device 100 according to thesecond embodiment of the present technology.

FIG. 35 is a flowchart showing the process procedure of signalprocessing by the information processing device 100 according to thesecond embodiment of the present technology.

FIG. 36 is a flowchart showing the process procedure of signalprocessing by the information processing device 100 according to thesecond embodiment of the present technology.

FIG. 37 is a block diagram showing an example of a schematicconfiguration of a smartphone.

FIG. 38 is a block diagram showing an example of a schematicconfiguration of a car navigation device.

DESCRIPTION OF EMBODIMENTS

Hereinafter, preferred embodiments for implementing the presenttechnology (which will be referred to hereinafter as embodiments) willbe described. Description will be provided in the following order.

1. First embodiment (Example in which a timing at which a mesh path isto be updated is delayed at the time of reception of a signal)

2. Second embodiment (Example in which a signal is transmitted inunicast and broadcast)

3. Application example

1. First Embodiment Configuration Example of a Communication System

FIG. 1 is a diagram showing a system configuration example of acommunication system 200 according to a first embodiment of the presenttechnology.

The communication system 200 includes a plurality of informationprocessing devices (an information processing device 100, an informationprocessing device 210, an information processing device 220, aninformation processing device 230, and an information processing device240). Each of the information processing devices constituting thecommunication system 200 is, for example, a portable type informationprocessing device or a fixed type information processing device with awireless communication function. It should be noted that portable typeinformation processing devices include wireless communication devices,for example, smartphones, mobile telephones, tablet terminals, and fixedtype information processing devices include information processingdevices such as printers, personal computers, and the like.

In FIG. 1 rectangles representing the information processing devices arelabeled with reference symbols (A to E) for identifying the respectiveinformation processing devices. In other words, the rectanglerepresenting the information processing device 100 is labeled “A,” therectangle representing the information processing device 210 is labeled“B,” the rectangle representing the information processing device 220 islabeled “C,” the rectangle representing the information processingdevice 230 is labeled “D,” and the rectangle representing theinformation processing device 240 is labeled “E.” In addition, thereference symbols A to E are used to display the content of signalsexchanged between the information processing devices as shown in FIGS. 9to 20, and the like.

In addition, FIG. 1 shows communication paths between the informationprocessing device 100 and the information processing devices 210, 220,and 230 using dotted lines 251, 253, and 254. In addition, communicationpaths between the other information processing devices are likewiseindicated using dotted lines 252 and 255 to 257.

Here, as a communication method for autonomously connecting with anearby information processing device, ad hoc communication, an ad hocnetwork, and the like are known. On such a network, each informationprocessing device can perform communication with a nearby informationprocessing device without depending on a master station (for example, acontrol device). Thus, in this embodiment of the present technology, anad hoc network will be exemplified as a communication method forautonomously connecting with a nearby information processing device

When a new nearby information processing device is added on an ad hocnetwork, this new information processing device can freely participatein the network. For example, a case in which, among the informationprocessing devices shown in FIG. 1, only the information processingdevice 100, the information processing device 210, the informationprocessing device 220 first participate in the ad hoc network isassumed. In this case, the information processing device 230 and theinformation processing device 240 are assumed to be added in order. Inthis case, as the number of the information processing devices (nearbyinformation processing devices) increases, coverage of the network canbe widened. That is, according to the addition of the informationprocessing device 230 and the information processing device 240 inorder, coverage of the network can be widened.

Here, on top of autonomous connection with a nearby informationprocessing device, each information processing device can also transferinformation to be exchanged with another information processing devicein a bucket brigade manner.

It is assumed that, for example, the information processing device 100can directly communicate with each of the information processing devices210, 220, and 230, but is not able to directly communicate with theinformation processing device 240 for a reason such as radio wavesfailing to reach the device.

When direct communication is not possible as described above, theinformation processing devices which can directly communicate with theinformation processing device 100 (the information processing devices210, 220, and 230) can transfer data of the information processingdevice 100 to the information processing device 240. Thus, such transferof data enables the information processing device 100 and theinformation processing device 240 which does not directly communicatewith the information processing device 100 to exchange information viaany of the information processing devices 210, 220, and 230.

This method of performing data transfer between devices (so-calledbucket brigade) as described above to cause information to reach aremote information processing device is called multi-hop relay. Inaddition, a network which performs multi-hop is generally known as amesh network.

A configuration of an information processing device which constitutessuch an ad hoc network or a mesh network is shown in FIG. 2. Inaddition, multi-hop relay will be described in more detail withreference to FIGS. 4 to 20, and the like.

In addition, among the information processing devices which constitutethe communication system 200 in the embodiments of the presenttechnology, an information processing device which serves as a reference(for example, an information processing device which receives a signal)will be referred to as a self-station, and other information processingdevices will be referred to as a transmitting station, a receivingstation, a transmission source station, a destination station, and anearby station.

In more detail, an information processing device which transmits asignal received by the self-station will be referred to as atransmitting station, and an information processing device whichreceives a signal from the self-station will be referred to as areceiving station. In addition, a transmission source informationprocessing device which first transmits a signal received by theself-station (a so-called leader of a bucket brigade) will be referredto as a transmission source station, and an information processingdevice which receives a signal received by the self-station in the end(a so-called terminus of the bucket brigade) will be referred to as adestination station. In addition, an information processing device whichtransfers a signal received by the self-station will be referred to as arelay station, and an information processing device which is near or inthe vicinity of the self-station on a network will be referred to as anearby station.

[Configuration Example of an Information Processing Device]

FIG. 2 is a block diagram showing an internal configuration example ofthe information processing device 100 according to the first embodimentof the present technology. Herein, only the information processingdevice 100 will be described because internal configurations of theother information processing devices (the information processing devices210, 220, 230, and 240) are the same as that of the informationprocessing device 100, and thus other information processing deviceswill not be described.

The information processing device 100 includes an antenna 110, acommunication unit 120, an input/output (I/O) interface 130, a controlunit 140, and a memory 150. In addition, these units are connected toone another via a bus 160.

The communication unit 120 is a module (for example, a modem) forperforming transmission and reception of radio waves via the antenna110. For example, the communication unit 120 can perform wirelesscommunication through millimeter wave communication (60 GHz, etc.), awireless local area network (LAN) of 900 MHz, 2.4 GHz, or 5 GHz, or anultra-wide band (UWB). In addition, the communication unit 120 canperform wireless communication through, for example, visible lightcommunication or near field communication (NFC).

For example, the communication unit 120 exchanges a signal (an RANN, aPREQ, or a PREP) for generating or updating a communication path ofmulti-hop using wireless communication with another informationprocessing device based on control of the control unit 140. The RANN,PREQ, and PREP will be described in detail with reference to FIG. 4, andthe like.

It should be noted that the communication unit 120 may be designed toperform wireless communication using radio waves (electromagnetic waves)or wireless communication using a medium other than radio waves (forexample, wireless communication performed using a magnetic field).

In addition, the communication unit 120 performs communication with anearby information processing device by setting up a communication link,manages the number of nearby information processing devices with whichthe information processing device 100 can communicate, and retainsinformation which indicates the number of nearby communicableinformation processing devices (communicable device number information).Furthermore, the communication unit 120 regularly or irregularlyobserves a degree of use of a channel used in wireless communication,and retains information which indicates a level of congestion of acommunication line around the information processing device 100(congestion level information). In addition, the communication unit 120observes link quality (reception power, a transmittable data rate, etc.)with a nearby information processing device performing wirelesscommunication therewith, and retains information which indicates abandwidth which makes wireless communication with a nearby informationprocessing device possible (communication state information). Then, thecommunication unit 120 supplies the information to the control unit 140.

The I/O interface 130 is an interface with an external device such as asensor actuator which operates in linkage with the informationprocessing device 100. FIG. 2 shows an example in which, for example, amovement detection unit 171, an operation reception unit 172, a displayunit 173, and an audio output unit 174 are connected with the I/Ointerface 130 as external devices. In addition, FIG. 2 shows the examplein which the movement detection unit 171, the operation reception unit172, the display unit 173, and the audio output unit 174 are providedoutside the information processing device 100, but all or some of theunits may be installed inside the information processing device 100.

The movement detection unit 171 detects a movement of the informationprocessing device 100 by detecting acceleration, a motion, aninclination, or the like of the information processing device 100, andoutputs movement information regarding the detected movement to thecontrol unit 140 via the I/O interface 130. For example, the movementdetection unit 171 retains movement information which indicates whetheror not the information processing device 100 is moving to a differentplace (a log (or real-time information regarding the movement)), andsupplies the information to the control unit 140. As the movementdetection unit 171, for example, an acceleration sensor, a gym sensor,or the Global Positioning System (GPS) can be used. The movementdetection unit 171 can compute a movement distance of the informationprocessing device 100 (for example, a movement distance per unit time)using, for example, position information (for example, latitude andlongitude) detected using the GPS.

The operation reception unit 172 is an operation reception unit whichreceives an operation input performed by a user, and outputs operationinformation according to the received operation input to the controlunit 140 via the I/O interface 130. The operation reception unit 172 isrealized with, for example, a touch panel, a keyboard, or a mouse.

The display unit 173 is a display unit on which various kinds ofinformation are displayed based on control of the control unit 140. Asthe display unit 173, for example, a display panel such as an organicelectro luminescence (EL) panel, or a liquid crystal display (LCD) canbe used. The operation reception unit 172 and the display unit 173 canbe configured to be integrated using a touch panel on which operationscan be input by a user bringing his or her finger in contact with orclose to its display plane.

The audio output unit 174 is an audio output unit (for example, aspeaker) which outputs various kinds of sounds based on control of thecontrol unit 140.

The control unit 140 controls each unit of the information processingdevice 100 based on a control program stored in the memory 150. Thecontrol unit 140 performs, for example, signal processing of transmittedand received information. In addition, the control unit 140 is realizedwith a central processing unit (CPU).

The memory 150 is a memory which stores various kinds of information.For example, the memory 150 stores various kinds of informationnecessary for the information processing device 100 to perform a desiredoperation (for example, the control program). In addition, the memory150 stores, for example, the mesh path table 350 shown in FIG. 21.Furthermore, the memory 150 stores various kinds of content such asmusic content and image content (for example, dynamic image content andstill image content).

When data is transmitted using wireless communication, for example, thecontrol unit 140 processes information read from the memory 150, asignal input from the I/O interface 130, or the like, and generates amass of data to be actually transmitted (transmission packets).Successively, the control unit 140 outputs the generated transmissionpackets to the communication unit 120. In addition, the communicationunit 120 converts the transmission packets in a format of acommunication scheme for actual transfer or the like, and transmits theconverted transmission packets to the outside from the antenna 110.

In addition, when data is received using wireless communication, forexample, the communication unit 120 extracts reception packets of radiowaves received via the antenna 110 through signal processing performedby a receiver inside the communication unit 120. Then, the control unit140 analyzes the extracted reception packets. When the packets aredetermined to be data to be retained as a result of the analysis, thecontrol unit 140 writes the data in the memory 150. In addition, whenthe packets are determined to be data to be transferred to anotherinformation processing device, the control unit 140 outputs the data tothe communication unit 120 as transmission packets to be transmitted toanother information processing device. Furthermore, when the packets aredetermined to be data to be transferred to an external actuator, thecontrol unit 140 outputs the packets to the outside (for example, thedisplay unit 173) from the I/O interface 130.

The control unit 140 can, for example, provide various kinds of contentstored in the memory 150 to another information processing device usingwireless communication.

It should be noted that, when the information processing device 100 isdriven by a battery, a battery is mounted (installed or loaded) in theinformation processing device 100. In this case, the control unit 140has a function of estimating a remaining battery amount, and thus canacquire the estimated remaining battery amount as needed.

[Example of a Signal Format]

FIG. 3 is a diagram showing an example of a signal format of a packetexchanged between information processing devices which constitute thecommunication system 200 according to the first embodiment of thepresent technology.

Here, each of the information processing devices constituting thecommunication system 200 exchanges signals in a packet form duringcommunication. The signal in the packet form includes at least two typesincluding a management packet and a data packet. Thus, a of FIG. 3 showsan example of the signal format of a management packet and b of FIG. 3shows the signal format of a data packet.

The management packet shown in a of FIG. 3 is a packet used forgenerating and retaining a network.

As shown in a of FIG. 3, the transmission signal of the managementpacket is composed of a header part (301 to 303) and a payload part 304.In addition, there are three fields in the header part. These threefields are a Frame Control field 301, an RX STA ADDR field 302, and a TXSTA ADDR field 303.

In the leading part of the header part, there is the Frame Control field301 in which an attribute of a signal including this header and the likeare stored. Each information processing device can acquire informationof whether a packet is a data packet or a management packet for controland management and the like with reference to the Frame Control field301.

In the RX STA ADDR field 302, an identifier (address) indicating apacket receiving station is stored. Each information processing devicecan know which information processing device is supposed to receive thesignal (packet) with reference to the RX STA ADDR field 302. Aninformation processing device which has received the signal (packet)starts a reception process of the received signal (packet) when, forexample, content of the RX STA ADDR field 302 is its own identifier(address) or a broadcast address.

In the TX STA ADDR field 303, an identifier (address) of a packettransmitting station. Each information processing device can recognizewhich information processing device has transmitted the signal withreference to the TX STA ADDR field 303.

The data packet shown in b of FIG. 3 is a packet used when applicationdata or the like is transmitted.

As shown in b of FIG. 3, the transmission signal of the data packet iscomposed of a header part (305 to 309) and a payload part 310. Inaddition, there are 5 fields in the header part. These 5 fields are aFrame Control field 305, an RX STA ADDR field 306, a TX STA ADDR field307, a Dst STA ADDR field 308, and an Src STA ADDR field 309.

In the leading part of the header part, there is the Frame Control field305 in which an attribute of a signal including this header and the likeare stored. Each information processing device can acquire informationof whether a packet is a data packet or a management packet for controland management and the like with reference to the Frame Control field305.

In the RX STA ADDR field 306, an identifier (address) indicating apacket receiving station is stored. Each information processing devicecan know which information processing device is supposed to receive thesignal (packet) with reference to the RX STA ADDR field 306. Aninformation processing device which has received the signal (packet)starts a reception process of the received signal (packet) when, forexample, content of the RX STA ADDR field 306 is its own identifier(address) or a broadcast address.

In the TX STA ADDR field 307, an identifier (address) of a packettransmitting station. Each information processing device can recognizewhich information processing device has transmitted the signal withreference to the TX STA ADDR field 307.

In the Dst STA ADDR field 308, an identifier (address) indicating apacket destination station (an information processing device which issupposed to receive the packet in the end) is stored. Each informationprocessing device can know to which information processing device thesignal is supposed to be transmitted in the end with reference to theDst STA ADDR field 308. An information processing device which hasreceived the signal performs a transfer process to transmit the receivedsignal to a destination station when, for example, the Dst STA ADDRfield 308 does not include its own identifier (address).

In the Src STA ADDR field 309, an identifier (address) of a packettransmission source station (an information processing device whichfirst transmitted the packet first) is stored. For example, eachinformation processing device can recognize which information processingdevice has transmitted the signal with reference to the Src STA ADDRfield 309.

Here, when data destined for a specific information processing device istransferred through the above-described multi-hop relay, it is necessaryto decide a path on which the data is to be relayed before the data istransferred. This procedure is called path selection. In addition, inthis path selection, a communication path is decided by exchanging amanagement signal between information processing devices for selecting apath. It should be noted that a communication path on a mesh network iscalled a mesh path. In FIGS. 4 to 7, types and formats of managementsignals used for generating this mesh path are shown.

[Examples of Signal Formats]

FIG. 4 is a diagram showing an example of a signal format of amanagement packet exchanged between the information processing deviceswhich constitute the communication system 200 according to the firstembodiment of the present technology.

FIGS. 5 to 7 are diagrams showing examples of the content of the signalformats of the management packet exchanged between the informationprocessing devices which constitute the communication system 200according to the first embodiment of the present technology. In otherwords, FIGS. 5 to 7 show the examples of the content of the signalformats of the management packets shown in FIG. 4.

a of FIG. 4 shows the management packet. This management packet is thesame as that of a of FIG. 3. As described above, the Frame Control field301 of the management packet stores the fact that the signal is amanagement packet.

b to d of FIG. 4 show a configuration example of the payload part 304 ofthe management packet shown in a of FIG. 4. Specifically, b of FIG. 4shows a configuration example of a case in which the management packetis an RANN (root announcement signal). In addition, c of FIG. 4 shows aconfiguration example of a case in which the management packet is a PREQ(path request signal). Also, d of FIG. 4 shows a configuration exampleof a case in which the management packet is a PREP (path reply signal).

The RANN (root announcement signal) shown in b of FIG. 4 is a signalused for proactively generating a mesh path regardless of presence oftransmission data. Here, the case in which a mesh path is proactivelygenerated is a case in which, regardless of necessity of data transfer,a mesh path between a specific information processing device and anotherinformation processing device on a network is generated beforehand.

As shown in b of FIG. 4, there are a plurality of fields (311 to 318) inthe RANN.

In the Length field 311, information indicating the length of thepayload is stored.

In the ActionType field 312, an identifier indicating that the signal isan RANN is stored. An information processing device which has receivedthe signal can recognize that the received signal is an RANN withreference to the ActionType field 312.

In the Flags field 313, an attribute of a transmission source station ofthe RANN (information processing device which has transmitted the RANNfirst) is stored. This attribute is information indicating, for example,a role of the information processing device. For example, when theinformation processing device which has transmitted the RANN first(transmission source station) is a device for causing anotherinformation processing device to be connected to the Internet, the Flagsfield 313 stores that fact.

In the OrigSTA field 314, an identifier (address) indicating whichinformation processing device is the transmission source station of theRANN (information processing device which has transmitted the RANNfirst) is stored. Here, although the RANN is transferred to a remotespot through multi-hop relay, an information processing device which hasreceived the RANN can recognize which information processing device isthe transmission source station of the received RANN with reference toOrigSTA field 314.

In the SeqNum field 315, an identifier for identifying the RANN isstored. For example, each time the RANN is transmitted from thetransmission source station, an incremented value is stored in theSeqNum field 315. In other words, as the RANN is regularly orirregularly transmitted from the transmission source station, aninformation processing device which has received the RANN can recognizewhether or not the received RANN is the same RANN as that receivedbefore with reference to the SeqNum field 315.

In the HopCount field 316, a numerical value indicating the number ofhops necessary for the RANN to be delivered from the transmission sourcestation (information processing device which has transmitted the RANNfirst) is stored. An information processing device which has receivedthe RANN transfers the received RANN in multi-hop, and an incrementedvalue is stored in the HopCount field 316 with each the transferprocess.

In the Metric field 317, a value indicating a metric value that wasnecessary for arrival of the RANN from the transmission source station(information processing device which has transmitted the RANN first) isstored. An information processing device which has received the RANNtransfers the received RANN in multi-hop, and the Metric field 317stores a value obtained by cumulatively adding metric values of a linkbetween information processing devices with each transfer process.

Here, a metric value of a link between information processing devices isa value indicating, for example, at how many Mbps transfer is possibleon that link. In the IEEE standard 802.11-2012, for example, a metricvalue ca can be obtained from the following expression 1.

ca=[O+(Bt/r)]/[1/(1−ef)]  Expression 1

Here, r is a value indicating a data rate (Mb/s). In addition, ef is avalue indicating a frame error rate. Further, Bt is a value indicating aframe size. Also, O is an intrinsic value of a physical layer (PHY).

In the Etc field 318, other management information is stored.

The PREQ (path request signal) shown in c of FIG. 4 is a signal used forrequesting generation of a mesh path destined for a specific informationprocessing device.

As shown in c of FIG. 4, there are a plurality of fields (319 to 328) inthe PREQ.

In the Length field 319, information indicating the length of thepayload is stored.

In the ActionType field 320, an identifier indicating that the signal isa PREQ is stored. An information processing device which has receivedthe signal can recognize that the received signal is a PREQ withreference to the ActionType field 320.

In the Flags field 321, information indicating whether the PREQ has beentransmitted triggered by reception of the RANN (whether this is aproactive mesh path generation process) is stored.

In the OrigSTA field 322, an identifier (address) indicating aninformation processing device serving as a requesting source of meshpath generation (transmission source station) is stored. Here, althoughthe PREQ is transferred to a remote spot through multi-hop relay, aninformation processing device which has received the PREQ can recognizewhich information processing device is the transmission source stationof the received PREQ with reference to the OrigSTA field 322.

In the DestSTA field 323, an identifier indicating an informationprocessing device serving as a request destination of mesh pathgeneration (destination station) is stored. When an informationprocessing device specified with the identifier stored in the DestSTAfield 323 (destination station) receives the PREQ, the device replieswith a PREP in response thereto. Accordingly, a bidirectional mesh pathis generated.

In the SeqNum field 324, an identifier for identifying the PREQ isstored. For example, each time the PREQ is transmitted from thetransmission source station, an incremented value is stored in theSeqNum field 324. In other words, there are cases in which, although thePREQ is transmitted from the transmission source station a plurality oftimes, an information processing device which has received the PREQ canrecognize whether or not the received PREQ is the same one as a PREQreceived before with reference to the SeqNum field 324.

In the HopCount field 325, a numerical value indicating the number ofhops necessary for the PREQ to be delivered from the transmission sourcestation (information processing device which has transmitted the PREQfirst) is stored. An information processing device which has receivedthe PREQ transfers the received PREQ in multi-hop, and an incrementedvalue is stored in the HopCount field 325 with each the transferprocess.

In the Metric field 326, a value indicating a metric value that wasnecessary for arrival of the PREQ from the transmission source station(information processing device which has transmitted the PREQ first) isstored. An information processing device which has received the PREQtransfers the received PREQ in multi-hop, and the Metric field 326stores a value obtained by cumulatively adding metric values of a linkbetween information processing devices with each transfer process.

In the Lifetime field 327, information indicating a lifetime of a meshpath is stored. In other words, when a mesh path generation requestsucceeds, a valid mesh path (active mesh path) is generated, and a valuefor specifying the lifetime of the mesh path is stored in the Lifetimefield 327.

In the Etc field 328, other management information is stored.

The PREP (path reply signal) shown in d of FIG. 4 is a signal used forreply to a request to generate a mesh path destined for a specificinformation processing device.

As shown in d of FIG. 4, there are a plurality of fields (329 to 338) inthe PREP.

In the Length field 329, information indicating the length of thepayload is stored.

In the ActionType field 330, an identifier indicating that the signal isa PREP is stored. An information processing device which has receivedthe signal can recognize that the received signal is a PREP withreference to the ActionType field 330.

In the Flags field 331, an attribute of a transmission source station ofthe PREP (an information processing device which has transmitted thePREP first) is stored.

In the OrigSTA field 332, an identifier indicating an informationprocessing device serving as a requesting source for generating a meshpath is stored. Here, the identifier of the information processingdevice stored in the OrigSTA field 322 of the PREQ (transmission sourcestation of the PREQ) is transcribed in the OrigSTA field 332.

In the DestSTA field 333, an identifier indicating an informationprocessing device serving as a request destination for generation of themesh path is stored. Here, the identifier of the information processingdevice stored in the DestSTA field 323 of the PREQ (destination stationof the PREQ) is transcribed in the DestSTA field 333.

In the SeqNum field 334, an identifier for identifying the PREP isstored. For example, each time the PREP is transmitted from thetransmission source station, an incremented value is stored in theSeqNum field 334. In other words, there are cases in which, although thePREP is transmitted from the transmission source station a plurality oftimes, a destination station which has received the PREP can recognizewhether or not the received PREP is the same one as a PREP receivedbefore with reference to the SeqNum field 334.

In the HopCount field 335, a numerical value indicating the number ofhops necessary for the PREP to be delivered from the transmission sourcestation of the PREP is stored. An information processing device whichhas received the PREP transfers the received PREP in multiple-hop, andan incremented value is stored in the HopCount field 335 with eachtransfer process.

In the Metric field 336, a value indicating a metric value that wasnecessary for arrival of the PREP from the transmission source stationis stored. An information processing device which has received the PREPtransfers the received PREP in multi-hop, and the Metric field 336stores a value obtained by cumulatively adding metric values of a linkbetween information processing devices with each transfer process.

In the Lifetime field 337, information indicating a lifetime of a meshpath is stored. In other words, when a mesh path generation requestsucceeds, a valid mesh path (active mesh path) is generated, and a valuefor designating the lifetime of the mesh path is stored in the Lifetimefield 337.

In the Etc field 338, other management information is stored.

The information processing devices constituting the communication system200 generate path information (also referred to as transfer informationor mesh path information) necessary during multi-hop communication byexchanging the RANN, the PREQ, and the PREP. For example, theinformation processing devices generates a multi-hop communication pathat a fixed time interval or irregularly by exchanging the RANN, thePREQ, and the PREP. In addition, the path information is pathinformation for specifying the next information processing device towhich packets should be transferred in order to deliver the packets to adestination information processing device. This path information isretained inside each information processing device as a mesh path table.In addition, when transmitting data packets to a specific informationprocessing device, each information processing device decides aninformation processing device to be designated as a receiving station totransmit the packets with reference to the mesh path table. In otherwords, when transmitting data packets to a specific informationprocessing device, each information processing device decides whatinformation processing device should be designated in the RX STA ADDRfield 302 to transmit the packets with reference to the mesh path table.This mesh path table will be described in detail with reference to FIGS.8, 21, and 22.

[Configuration Example of a Mesh Path Table]

FIG. 8 is a diagram schematically showing an example of a mesh pathtable (mesh path table 340) retained by each information processingdevice which constitutes the communication system 200 according to thefirst embodiment of the present technology.

a of FIG. 8 schematically shows a configuration of the mesh path table340, and b of FIG. 8 shows an example of the content of the mesh pathtable 340. Specifically, b of FIG. 8 shows an Index 346, a data name347, and a meaning 348 as the example of the content of the mesh pathtable 340.

As shown in a of FIG. 8, the mesh path table 340 is recorded in thememory 150 in a record form. In addition, the mesh path table 340 isdesigned such that each record can be extracted therefrom using theaddress (Dest 341) of a destination station as a key. In addition, asrecords of the mesh path table 340, a NextHop 342, a Metric 343, aSeqNum 344, and an ExpTime 345 are stored. It should be noted that, in bof FIG. 8, reference symbols a to d for identifying each of the recordsare given in the Index 346.

In the NextHop 342 of “a” of the Index 346, an identifier of aninformation processing device indicating to what information processingdevice data should be transferred next in order to deliver the data to adestination station is stored. In other words, the NextHop 342 stores anidentifier of a transmitting station.

In the Metric 343 of “b” of the Index 346, a path metric value from aself-station to the destination station of the mesh path is stored. Acomputation method for this path metric value will be shown in FIGS. 9,10, etc.

In the SeqNum 344 of “c” of the Index 346, the value of SeqNum of thePREQ or the PREP (for example, the SeqNum fields 324 and 334 shown in cand d of FIG. 4) used to generate the mesh path is stored.

In the ExpTime 345 of “d” of the Index 346, the expiration time of themesh path is stored. The expiration time of the mesh path is decidedbased on the Lifetime fields 327 and 337 of the PREQ or the PREP (shownin c and d of FIG. 4) used to generate the mesh path.

Each information processing device constituting the communication system200 generates path information at the time of a request of generation ofa path or a reply thereto, and writes the generated path information inthe mesh path table 340. In addition, when transferring data, based onthe address (Dest 341) of a destination station to which the data is tobe delivered, each information processing device constituting thecommunication system 200 extracts a record corresponding to thedestination station from the mesh path table 340. In addition, theinformation processing device performs a transfer process fortransferring the data to a transmitting station corresponding to theNext-op 342 of the extracted record.

[Generation Example of a Reactive Mesh Path]

FIGS. 9 and 10 are diagrams showing a generation example of a reactivemesh path retained by each information processing device constitutingthe communication system 200 according to the first embodiment of thepresent technology.

In FIGS. 9 and 10, the procedure for generating the mesh path table 340using a PREQ and a PREP will be described. Specifically, in FIGS. 9 and10, a case in which, when the information processing device 100 attemptsto transmit data destined for the information processing device 240 inthe topology shown in FIG. 1, the information processing device 100requests generation of a mesh path between the information processingdevice 240 will be described.

As shown in a of FIG. 9, the information processing device 100 transmitsa PREQ in which the information processing device 240 has beendesignated in the Dest STA field 323 (shown in c of FIG. 4). Aconfiguration of the PREQ has been shown in c of FIG. 4 and FIG. 6. Inaddition, when the PREQ is transmitted, the control unit 140 of theinformation processing device 100 stores zero as an initial value in theHopCount field 325 and the Metric field 326 of the PREQ to betransmitted. Furthermore, the control unit 140 of the informationprocessing device 100 stores a value obtained by incrementing the valuestored in the PREQ that was transmitted the previous time in the SeqNumfield 324 of the PREQ to be transmitted. In addition, the control unit140 of the information processing device 100 sets a broadcast addressfor designating each information processing device located nearby as areceiving station in the RX STA ADDR field 303 (shown in a of FIG. 4) ofthe management packet of the PREQ to be transmitted.

It should be noted that, in a of FIG. 9, the flow of the PREQtransmitted from the information processing device 100 to eachinformation processing device is schematically shown with thick-linearrows. In addition, the name of the signal (PREQ), the reference symbolof the destination station (Dest-E), and the reference symbol of thetransmission source station and relay station (including thetransmitting station) of the PREQ (A) are given to the thick-linearrows.

For example, PREQ Dest=E(A) shown in a of FIG. 9 means that it is a PREQof which the destination station is the information processing device240 and the transmission source station and the relay station (includingthe transmitting station) are the information processing device 100. Itshould be noted that the same applies to the names and reference symbolsof thick-line arrows in the following drawings.

As shown in a of FIG. 9, the information processing devices 210, 220,and 230 receive the PREQ transmitted from the information processingdevice 100. Upon receiving the PREQ, the information processing devices210, 220, and 230 generate mesh path information destined for aninformation processing device (destined for the information processingdevice 100) of which the identifier is stored in the OrigSTA field 322of the received PREQ. In addition, the information processing devices210, 220, and 230 records the generated mesh path information in themesh path table 340 as mesh path information destined for theinformation processing device 100.

In this case, each information processing device stores the identifier(address) of the information processing device 100 in the Dest 341 ofthe mesh path table 340. In addition, each information processing devicestores the identifier (address) of the TX STA ADDR field 303 of thereceived PREQ in the NextHop 342 of “a” of the Index 346 of the meshpath table 340.

Furthermore, each of the information processing devices acquires ametric value of a link between a transmitting station of the receivedPREQ and the self-device. For example, the information processing device210 acquires a metric value of a link between the transmitting station(the information processing device 100) of the received PREQ and theself-device (the information processing device 210). Subsequently, eachinformation processing device computes a path metric value by adding theacquired metric value of the link to the value stored in the Metricfield 326 of the received PREQ. Then, each information processing devicestores the computed path metric value in the Metric 343 of “b” of theIndex 346 of the mesh path table 340.

Here, the transmitting station of the received PREQ is the informationprocessing device corresponding to the identifier stored in the TX STAADDR field 303, and is the information processing device 100 in theexample shown in FIG. 9. In addition, the metric value of the linkbetween the transmitting station of the received PREQ and theself-device is, for example, a value which indicates at how many Mbpstransfer is possible on that link.

Furthermore, each information processing device stores the value of theSeqNum field 324 of the received PREQ in the SeqNum 344 of “c” of theIndex 346 of the mesh path table 340.

In addition, each information processing device stores the valueobtained by adding the value stored in the Lifetime field 327 of thePREQ to the reception time of the PREQ (expiration time) in the ExpTime345 of “d” of the Index 346 of the mesh path table 340. The mesh pathgenerated in that manner is referred to as a value mesh path until theexpiration time stored in the ExpTime 345 of “d” of the Index 346 of themesh path table 340.

In this manner, the information processing devices 210, 220, and 230generate the mesh path destined for the information processing device100.

Furthermore, as shown in b of FIG. 9, the respective informationprocessing devices 210, 220, and 230 which have received the PREQtransfer the received PREQ because the identifier of the DestSTA field323 of the received PREQ is not theirs. At the time of this transfer,the information processing devices 210, 220, and 230 increment the valueof the HopCount field 325 of the received PREQ. Then, the previouslycalculated path metric value is stored in the Metric field 326, and thevalue of the received PREQ is transcribed in the field of another PREQ.In addition, the information processing devices 210, 220, and 230 set abroadcast address for designating each information processing devicelocated nearby as a receiving station in the RX STA ADDR field 302.

Upon receiving the transferred PREQ, for example, the informationprocessing device 240 generates mesh path information destined for theinformation processing device (destined for the information processingdevice 100) of which the identifier is stored in the OrigSTA field 322of the received PREQ in the above-described procedure. Then, theinformation processing device 240 records the generated mesh pathinformation in the mesh path table 340 as mesh path information of whichthe recipient is set to the information processing device 100.

Here, as shown in b of FIG. 9, the information processing device 240receives such PREQ signals from the information processing devices 220and 230. When the PREQ signal has received from a plurality ofinformation processing devices in this manner, the informationprocessing device 240 selects a path having a low path metric value as avalid mesh path, and discards a PREQ having a high path metric value.

In the example shown in FIG. 9, a case in which the path metric value ofthe PREQ transferred from the information processing device 230 is lowerthan the path metric value of the PREQ transferred from the informationprocessing device 220 is assumed. In this case, the informationprocessing device 240 generates a mesh path of which the NextHop 342 isset to the information processing device 230 as a mesh path designed forthe information processing device 100.

In addition, since the information processing device 240 designatesself-device as the DestSTA field 323 of the received PREQ, the devicegenerates a PREP for replying to this PREQ. Thus, as shown in a of FIG.10, the information processing device 240 transmits the generated PREPsignal by designating the NextHop destined for the OrigSTA field 322 ofthe PREQ as a receiving station.

In this case, the information processing device 240 transcribes thevalues stored in the PREQ in the OrigSTA field 332 and the DestSTA field333, and stores zero as an initial value in the HopCount field 335 andthe Metric field 336. In addition, the information processing device 240stores in the SeqNum 344 the value obtained by incrementing the valuestored in the previously transmitted PREQ or PREP. In addition, theinformation processing device 240 sets the NextHop destined for OrigSTAof the PREQ (the information processing device 230 in this case) in theRX STA ADDR field 302 for transmission to the information processingdevice 230 in unicast.

Upon receiving the PREP transmitted from the information processingdevice 240, the information processing device 230 generates mesh pathinformation destined for an information processing device (destined forthe information processing device 240) of which the identifier is storedin the DestSTA field 333 of the received PREP in the above-describedprocedure. Then, the information processing device 230 records thegenerated mesh path information in the mesh path table 340 as mesh pathinformation of which the destination is set to the informationprocessing device 240. In this manner, upon receiving the PREPtransmitted from the information processing device 240, the informationprocessing device 230 generates a mesh path destined for the informationprocessing device 240.

As shown in b of FIG. 10, the identifier of the OrigSTA field 332 of thereceived PREP is not of the information processing device 230 which hasreceived the PREP. For this reason, the information processing device230 transfers the received PREP to the information processing devicewhich corresponds to the identifier of the OrigSTA field 332 of thereceived PREP. At the time of this transfer, the information processingdevice 230 increments the value of the HopCount field 335 of thereceived PREP. Then, a path metric value calculated in theabove-described procedure is stored in the Metric field 336, and thevalue of the received PREP is transcribed in the field of another PREP.In addition, in order to transmit the PREP in unicast, the informationprocessing device 230 sets the address of the NextHop 342 of the meshpath destined for the information processing device 100 (the address ofthe information processing device 100) in the RX STA ADDR field 302.Accordingly, unicast transmission of the PREP from the informationprocessing device 230 to the information processing device 100 isperformed as shown in b of FIG. 10.

Upon receiving the PREP transmitted from the information processingdevice 230, the information processing device 100 generates mesh pathinformation destined for the information processing device of which theidentifier is stored in the DestSTA field 333 of the received PREP(destined for the information processing device 240) in theabove-described procedure. Then, the information processing device 100records the generated mesh path information in the mesh path table 350as mesh path information of which the destination is set to theinformation processing device 240.

In this manner, the information processing device 100 generates a meshpath destined for the information processing device 240. In addition,since the identifier of the OrigSTA field 332 of the received PREP is ofthe information processing device 100, the device finishes thebi-directional mesh path generation procedure between the informationprocessing device 100 and the information processing device 240 withoutperforming a successive transfer process.

Thereafter, the mesh path records generated and retained in each of theinformation processing devices can be referred to before the expirationtime (ExpTime 345) of the generated mesh path elapses. For this reason,before the expiration time elapses, when data is exchanged between theinformation processing device 100 and the information processing device240, the mesh path records retained in each of the informationprocessing devices can be referred to perform communication in multi-hoprelay.

[Generation Example of a Proactive Mesh Path]

As described above, generation of a reactive mesh path is started whenactual transfer of data is necessary. However, regardless of necessityof data transfer, there is a technique of generating a mesh path inadvance between a specific information processing device and anotherinformation processing device on a network. This technique is calledproactive mesh path generation. When, for example, there is a gatewayconnected to an external network on a mesh network and a device isconnected to the Internet from the gateway, it is convenient to create amesh path between an information processing device functioning as agateway in advance. For this reason, there are cases in which aproactive mesh path is generated. Thus, in FIGS. 11 to 13, an example ofgenerating a proactive mesh path will be described.

FIGS. 11 to 13 are diagrams showing the example of generation of aproactive mesh path by the information processing devices whichconstitute the communication system 200 according to the firstembodiment of the present technology. In FIGS. 11 and 13, an example inwhich the information processing device 100 has a gateway function andthe information processing device 100 operates as a root station of apath is shown.

As shown in a of FIG. 11, in generation of a proactive mesh path, theinformation processing device 100 operating as a root station of a pathregularly or irregularly transmits an RANN (root announcement signal) inbroadcast. In other words, for transmission of an RANN, the address ofbroadcast is stored in the RX STA ADDR field 302.

In addition, as shown in b and c of FIG. 4, the RANN is substantiallythe same as the PREQ except for the fact that it does not have a DestSTAfield and a Lifetime field.

Furthermore, each process performed by each information processingdevice which has received the RANN is substantially the same as when thePREQ is received. In other words, each information processing devicewhich has received the RANN updates the HopCount field 316 and theMetric field 317 of the received RANN. Then, the updated RANN istransferred toward information processing devices located nearby inbroadcast as shown in b of FIG. 11.

Here, since the RANN is transmitted toward information processingdevices located nearby in broadcasting, each information processingdevice may receive the RANN from different information processingdevices a plurality of times. In such a case, a path metric value iscomputed with each reception of the RANN, and each process is performedusing only an RANN having a low path metric value as a valid RANN. Theinformation processing device (nearby information processing device)from which the RANN having the lowest path metric value has beentransmitted is ascertained, and the information processing device whichhas transmitted the RANN with the minimum value is recorded.

Each information processing device which has received the RANN transmitsa PREQ to generate a mesh path between the information processing deviceof which the identifier is stored in the OrigSTA field 314 of the RANN.In other words, each information processing device which has receivedthe RANN transmits a PREQ which stores the identifier of the OrigSTAfield 314 of the RANN in the DestSTA field 323.

Here, each information processing device has already ascertained viawhich information processing device (nearby information processingdevice) a signal should be transmitted to the information processingdevice of which the identifier is stored in the OrigSTA field 314 of thereceived RANN to minimize a path metric value. When the RANN is usedtogether to this end, an information processing device (nearbyinformation processing device) having the minimum path metric value isset as a receiving station and the PREQ is transmitted in unicast,rather than in broadcast. In this case, in the Flags field 321 of thePREQ, the fact that it is the PREQ transmitted due to the reception ofthe RANN is stored. In addition, a of FIG. 12 shows an example in whichthe information processing device 240 transmits the PREQ designating theinformation processing device 230 as a receiving station. Since eachprocess regarding the PREQ other than the above is the same as in thegeneration of the reactive mesh path, description will be omitted here.

In addition, as shown in b of FIG. 12, upon receiving the PREQ from theinformation processing device 240, the information processing device 230updates the mesh path destined for the information processing device240, and further transfers the PREQ to the information processing device100.

Furthermore, as shown in a of FIG. 13, upon receiving the PREQ from theinformation processing device 230, the information processing device 100updates the mesh path destined for the information processing device240, and replies with a PREP in response to the received PREQ.

In addition, as shown b of in FIG. 13, upon receiving the PREP from theinformation processing device 100, the information processing device 230updates the mesh path destined for the information processing device100, and further transfers the PREP to the information processing device240.

Upon receiving the PREP from the information processing device 230, theinformation processing device 240 updates the mesh path destined for theinformation processing device 100, and finishes the bi-directional meshpath generation procedure between the information processing device 240and the information processing device 100.

It should be noted that, as a technology for configuring such a wirelessnetwork system described above, the IEEE standard 802.11-2012 (IEEEStandard for Information Technology—Telecommunications and informationexchange between systems—Local and metropolitan area networks—Specificrequirements Part 11: Wireless LAN Medium Access Control (MAC) andPhysical Layer (PHY) Specifications) is widely known.

[Regarding Generation and Maintenance Management of a Mesh Path]

As described above, each of the information processing devices whichconstitute the communication system 200 exchanges signals (PREQ, PREP,and RANN) to generate and perform maintenance management of a mesh path.Thus, it is important to more appropriately perform generation andmaintenance management of a mesh path by making a change or addition toeach of the processes. This point will be described below.

Here, the case in which respective information processing devices areplaced and links (indicated by the dotted lines 251 to 257) arestretched as shown in FIG. 1 is assumed. In this case, a metric value ofthe first link (indicated by the dotted line 251) is assumed to be 100,a metric value of the second link (indicated by the dotted line 252) tobe 100, and a metric value of the third link (indicated by the dottedline 253) to be 400. In addition, a metric value of the fourth link(indicated by the dotted line 254) is assumed to be 150, and a metricvalue of the fifth link (indicated by the dotted line 255) is assumed tobe 400. Further, a metric value of the sixth link (indicated by thedotted line 256) is assumed to be 100, and a metric value of the seventhlink (indicated by the dotted line 257) is assumed to be 200.

[Regarding Generation of a Reactive Mesh Path]

FIGS. 14 and 15 are diagrams showing an example of generation of areactive mesh path by each of the information processing devices whichconstitute the communication system 200 according to the firstembodiment of the present technology. In FIGS. 14 and 15, a case inwhich the information processing device 100 requests the informationprocessing device 220 to generate a mesh path is shown.

As shown in a of FIG. 14, the information processing device 100transmits a PREQ in which the information processing device 220 isdesignated in the DestSTA field 323 in broadcast. This PREQ is directlytransmitted to the information processing device 220. Thus, uponreceiving the PREQ, the information processing device 220 starts aresponse process with a PREP as shown in b of FIG. 14. Accordingly,generation of a mesh path between the information processing device 100and the information processing device 220 is completed.

After a mesh path is generated between the information processing device100 and the information processing device 220, when the informationprocessing device 210 transfers the received PREQ, the informationprocessing device 220 receives the PREQ as shown in a of FIG. 15.

Here, the metric value of the path passing through the informationprocessing device 210 (200 (=100+100)) is smaller than the metric valueof the link (400) between the information processing device 100 and theinformation processing device 220. For this reason, when upon receivingthe PREQ transmitted by the information processing device 210, theinformation processing device 220 starts the response process with thePREP again as shown in b of FIG. 15. Then, as the information processingdevice 210 transfers the PREP to the information processing device 100,the path between the information processing device 100 and theinformation processing device 220 passing through the informationprocessing device 210 (a path with a minimum metric value) can be set.

Before a path with a minimum metric value is set, however a wrong path(a path of which the metric value is not minimum) may be set as shown inFIG. 14.

Thus, an example for preventing a wrong path from being set will beshown in the embodiment of the present technology. For example, anexample in which a destination station of a PREQ sets a timer (timewindow) immediately after receiving the PREQ without replying with aPREP, and starts the response process with the PREP at the timing atwhich the timer ends will be shown in the first embodiment of thepresent technology.

[Regarding Generation of a Reactive Mesh Path]

FIG. 16 is a diagram showing an example of generation of a reactive meshpath by each of the information processing devices which constitute thecommunication system 200 according to the first embodiment of thepresent technology. In FIG. 16, a case in which the informationprocessing device 100 requests the information processing device 210 togenerate a mesh path is shown.

As shown in FIGS. 14 and 15, the case in which the path between theinformation processing device 100 and the information processing device220 passing through the information processing device 210 (path with theminimum metric value) is set is assumed. A case in which the informationprocessing device 100 requests the information processing device 210 toset a new mesh path in that state is assumed.

As shown in FIG. 16, the information processing device 100 transmits aPREQ in which the information processing device 210 is designated in theDestSTA field 323 in broadcast. This PREQ is also directly transmittedto the information processing device 220. For this reason, uponreceiving the PREQ, the information processing device 220 starts areception process of the PREQ. In other words, the informationprocessing device 220 generates (updates in this case) mesh pathinformation destined for the information processing device 100corresponding to the OrigSTA field 322 of the PREQ, and records theinformation in the mesh path table 340 as information to be recordedwith regard to the information processing device 100.

With these processes, set path information (the path between theinformation processing device 100 and the information processing device220 passing through the information processing device 210 (path with theminimum metric value)) is overwritten. In the case of overwriting asabove, there is concern of the information processing device 220 notbeing capable of communicating on the correct path (path with theminimum metric value).

Thus, in the first embodiment of the present technology, an example inwhich a record of a mesh path is retained as retained informationwithout being re-written when a PREQ is received, and the retainedinformation is reflected as information of the mesh path at the timingat which a PREP is transmitted will be shown.

[Regarding Generation of a Proactive Mesh Path]

FIGS. 17 and 18 are diagrams showing an example of generation of aproactive mesh path by each of the information processing devices whichconstitute the communication system 200 according to the firstembodiment of the present technology. In FIGS. 17 and 18, a case inwhich the information processing device 100 is a root station andregularly transmits an RANN will be shown.

As shown in a of FIG. 17, the information processing device 100transmits an RANN in broadcast. This RANN is directly transmitted to theinformation processing device 220. Thus, upon receiving the RANN, theinformation processing device 220 starts a transmission process of aPREQ to generate a proactive mesh path as shown in b of FIG. 17. Whenthe information processing device 100 transmits a PREP to theinformation processing device 220 in response thereto, generation of amesh path between the information processing device 100 and theinformation processing device 220 is completed.

Even after the mesh path is generated as above, the informationprocessing device 210 transfers the RANN as shown in a of FIG. 18. Uponreceiving the RANN transferred by the information processing device 210as above, the information processing device 220 starts the transmissionprocess of the PREQ again as shown in b of FIG. 18 because the pathpassing through the information processing device 210 has a lower metricvalue.

With these processes, the path between the information processing device100 and the information processing device 220 passing through theinformation processing device 210 (path with the minimum metric value)can be set. In generation of the proactive mesh path, however, a wrongpath (path of which the metric value is not minimum) may be set beforethe path with the minimum metric value is set as shown in FIG. 17.

Thus, an example for preventing a wrong path from being set will beshown in the embodiment of the present technology. For example, anexample in which a timer (time window) is set immediately after an RANNis received without transmitting a PREQ, and the response process of thePREQ is started at the timing at which the timer ends will be shown inthe first embodiment of the present technology.

[Regarding Updating of a Valid Mesh Path]

Herein, a case in which a valid mesh path of the path between theinformation processing device 100 and the information processing device220 passing through the information processing device 210 (path with theminimum metric value) is set is assumed.

As described above, an expiration time is set for a mesh path. However,when transmission and reception of data packets are being activelyperformed while the expiration time approaches, a process of refreshingthe mesh path before the mesh path becomes invalid may be performed.This refreshing process is realized by, for example, performing aprocess such as generating a PREQ with respect to a destination stationof a record of which the expiration time has been determined to beapproaching. Specifically, for example, an information processing devicerefers to a record of the mesh path table 340 during transfer of datapackets and determines whether or not the expiration time stored in theExpTime 345 is approaching. Then, when the expiration time is determinedto be approaching, the information processing device performs a processsuch as generating a PREQ to the destination station of the record.

Here, a set value of the ExpTime 345 is set based on values of theLifetime field 327 and 337 of the PREQ and a PREP thereto. Thus, it isassumed that a start for refreshing the mesh path (a generation processof the PREQ) simultaneously occurs in the information processing device100, the information processing device 210, and the informationprocessing device 220. When the start for refreshing the mesh path (thegeneration process of the PREQ) simultaneously occurs, a number ofmanagement signals for generating the mesh path are exchanged, whichincreases overhead of wireless communication.

Thus, an example in which unnecessary overhead is cut will be shown inthe embodiment of the present technology. For example, an example inwhich a condition for triggering a refreshing process for a mesh path ofwhich the expiration time is approaching is changed according to aposition of an information processing device which performs therefreshing process on the mesh path will be shown.

[Regarding Overhead Caused by Generation of Mesh Paths that PartiallyOverlap]

Herein, the case in which the mesh path of the path between theinformation processing device 100 and the information processing device220 passing through the information processing device 210 (the path withthe minimum metric value) is assumed. There is a case in which, afterthe mesh path is generated as above, the information processing device100 generates another mesh path with the information processing device210.

Here, in order for the information processing device 100 to generate amesh path with the information processing device 210, it is necessaryfor the information processing device 100 to transmit a PREQ in whichthe information processing device 210 is set in the DestSTA field 323.In this manner, in order for the information processing device 100 togenerate a mesh path with the information processing device 210,exchange of management signals for generating the mesh path occurs. Itis important to suppress overhead of the management signals to as low alevel as possible.

In addition, for the mesh path set between the information processingdevice 220 by the information processing device 100, the NextHop 342 ofthe information processing device 100 is set to the informationprocessing device 210. Thus, it is obvious that the NextHop 342 of theinformation processing device 100 destined for the informationprocessing device 210 is set to the information processing device 210.Even in such case, however, it is necessary for the informationprocessing device 100 to exchange a new management signal to generatethe mesh path between the information processing device 210.

Therefore, in the first embodiment of the present technology, an examplein which, when a mesh path is generated, a mesh path record destined foran information processing device which corresponds to NextHop is alsogenerated (temporarily retained and updated) will be shown. In addition,in the first embodiment of the present technology, an example in which,when a record of NextHop is updated, a refreshing process of a path isset to be triggered as late as possible will be shown.

[Regarding Updating of a Valid Mesh Path]

FIG. 19 is a diagram showing a case in which a valid mesh path is set inthe communication system 200 according to the first embodiment of thepresent technology. In FIG. 19, an example in which the valid mesh path(indicated by the thick lines 251 and 252) of the path between theinformation processing device 100 and the information processing device220 passing through the information processing device 210 (the path withthe minimum metric value) is shown.

FIG. 20 is a diagram schematically showing the flow of data when theinformation processing device 100 according to the first embodiment ofthe present technology updates the valid mesh path.

Here, a case in which, when the expiration time of the mesh path shownin FIG. 19 is approaching, the mesh path is refreshed and updated isassumed. In this case, the information processing device 100 transmits aPREQ in which the information processing device 220 is set in theDestSTA field 323 in broadcast as shown in a of FIG. 20 to refresh themesh path.

The information processing device 210 which has received the PREQtransmitted from the information processing device 100 transmits thePREQ in broadcast to transfer the received PREQ. In addition, theinformation processing device 220 which has received the PREQtransmitted by the information processing device 210 can select thecomet path passing through the information processing device 210, andthen perform the response process with a PREP.

However, a case in which the PREQ is not correctly transferred from theinformation processing device 100 to the information processing device220 is also assumed. For example, a case in which the PREQ is notcorrectly transferred for a reason such as collision with another signalis assumed.

Here, in broadcast transmission, when transfer depending on AutomaticRepeat Request (ARQ) is not performed, it is not possible to detectcollision of signals. Thus, when broadcast transmission of the PREQ fromthe information processing device 210 to the information processingdevice 220 fails as shown in b of FIG. 20 (indicated by a x mark), theinformation processing device 220 is unable to receive the PREQ.

In this case, based on the reception result of the PREQ transmitteddirectly from the information processing device 100, the informationprocessing device 220 generates a reply signal of a PREP and replieswith the PREP directly to the information processing device 100. In thiscase, through a mesh path refreshing process, a wrong path may be setinstead of a correct path.

In other words, rather than the path between the information processingdevice 100 and the information processing device 220 passing through theinformation processing device 210 (correct path), a path between theinformation processing device 100 and the information processing device220 not passing through the information processing device 210 (wrongpath) may be set.

Thus, in a second embodiment of the present technology, an example inwhich, when management information (a PREQ or an RANN) is transmitted toan information processing device which corresponds to NextHop of a validmesh path, the same management information is transmitted in broadcastand unicast will be shown. This example will be shown in the secondembodiment of the present technology.

[Configuration Example of a Mesh Path Table]

FIGS. 21 and 22 are diagrams schematically showing an example of a meshpath table (mesh path table 350) retained by each of the informationprocessing devices which constitute the communication system 200according to the first embodiment of the present technology.

In FIG. 21, a configuration of the mesh path table 350 is schematicallyshown, and in FIG. 22, an example of the content of the mesh path table350 is shown. Specifically, in FIG. 22, Index 346, data name 347, andmeaning 348 are shown as the example of the content of the mesh pathtable 350. It should be noted that the mesh path table 350 shown inFIGS. 21 and 22 is produced by adding new information to the mesh pathtable 340 shown in FIG. 8. Particularly, the information of thereference symbols f to k, n, p, and q is newly added information. Thus,the same reference symbols are given to the common parts in FIGS. 21 and22 with the mesh path table 340 shown in FIG. 8, and a part ofdescription thereof will be omitted. In addition, FIG. 21 corresponds toa of FIG. 8, and FIG. 22 corresponds to b of FIG. 8.

As shown in FIG. 21, the mesh path table 350 is recorded in the memory150 in a record form. For the sake of facilitating description in theembodiment of the present technology, an example in which the mesh pathtable 350 produced by adding new information to the mesh path table 340shown in FIG. 8 is managed as one table is shown. The newly addedinformation (the information of the reference symbols f to k, n, p, andq), however, may be managed as a separate table (or in a separatememory) from the mesh path table 340.

In the ProactiveFlag 351 of “e” of the Index 346, a flag indicatingwhether or not a mesh path is one that has been proactively generated isstored.

In the ActReason 352 of “f” of the Index 346, a value indicating onwhich position in the mesh path a self-device is located is stored. Asthis value, a value indicating, for example, whether the self-device wasOrigSTA, DestSTA, or a relay station of a certain number of hops fromthe OrigSTA when the mesh path was generated is stored.

In the Candidate (Cand.) Flag 353 of “g” of the Index 346, a flagindicating whether or not the information after “f” of the Index 346 isvalid is stored.

In the Cand. NextHop 354 of “h” of the Index 346, the identifier of aninformation processing device determined to be a NextHop candidatetoward the destination station of this record when a PREQ (or an RANN)has been received is stored. Here, the destination station of thisrecord refers to an information processing device of which theidentifier is stored in the OrigSTA of the received PREQ (or the RANN).

In the Cand. Metric 355 of “i” of the Index 346, a path metric valuecomputed when the PREQ (or the RANN) is received is stored. This pathmetric value refers to a path metric value to the destination station ofthis record (i.e., OrigSTA of the PREQ (or the RANN)).

In the Cand. SeqNum 356 of “j” of the Index 346, a value of the SeqNumof the PREQ (or the RANN) used when this record is generated is stored.

In the Cand. ExpTime 357 of “k” of the Index 346, an expiration timedecided based on Lifetime of the PREQ used when this record is generatedis stored.

In the Cand. ActReason 358 of “n” of the Index 346, a value indicating aposition on the mesh path at which the self-device is located is stored.As this value, for example, a value indicating whether the self-devicewas OrigSTA, DestSTA, or a relay node of a certain number of hops fromthe OrigSTA when the mesh path was generated is stored.

In the Cand. Neighbor (NB.) Metric 359 of “p” of the Index 346, a linkmetric value between a transmitting station of the PREQ (or the RANN)used when this record is used is stored.

In the Cand. NB. ExpTime 360 of “q” of the Index 346, an expiration timedecided based on Lifetime of the PREQ used when this record is used isstored.

These items (the reference symbols f to k, n, p, and q) are recorded fora record of the destination station which corresponds to OrigSTA of thePREQ or the RANN at the time of reception of the PREQ and the RANN. Inaddition, they are referred to as original data at the timing at whichthe PREP is transmitted when the mesh path is to be updated.

[Operation Example of an Information Processing Device]

Next, operation examples of an information processing device will bedescribed in detail with reference to drawings. It should be noted that,in each of the operation examples below, only the information processingdevice 100 will be described; however, the same can be applied tooperations of the other information processing devices.

[Processing Example when a PREQ is Received]

FIG. 23 is diagram showing an example of updating of the mesh path table350 retained by the information processing device 100 according to thefirst embodiment of the present technology. This updating will bedescribed in detail with reference to FIG. 24.

FIG. 24 is a flowchart showing an example of the process procedure ofsignal processing by the information processing device 100 according tothe first embodiment of the present technology.

Here, the information processing device requesting generation of a meshpath transmits a PREQ according to the above-described procedure. Thus,in FIG. 24, an example of the process procedure of a signal transmissionand reception process by the information processing device 100 which hasreceived the PREQ is shown. It should be noted that the same referencesymbols as those of the signal shown in FIG. 4 are given to those of thesignal shown in this example. In addition, the same reference symbols asthose of the mesh path table 350 shown in FIG. 21 are given to those ofthe mesh path table 350 shown in this example. In addition, the sameapplies to each reference symbol shown in each operation example below.

The control unit 140 of the information processing device 100 which hasreceived the PREQ computes the path metric value to an informationprocessing device (transmission source station) of which the identifieris stored in the OrigSTA field 322 of the received PREQ (Step S801). Forexample, the control unit 140 of the information processing device 100acquires the link metric value between the transmitting station whichhas transmitted the received PREQ (the information processing device ofwhich the identifier (address) is stored in the TX STA ADDR field 303)and the self-station. For example, the control unit 140 of theinformation processing device 100 can estimate the link metric valuebetween the transmitting station and the self-station based on aReceived Signal Strength Indicator (RSSI) of the current beacon. Forexample, a correspondence table of the RSSI and the metric value is heldbeforehand, and using this table, the metric value can be estimated fromthe RSSI. Next, the control unit 140 of the information processingdevice 100 adds the link metric value obtained from that addition to thevalue stored in the Metric field 326 of the received PREQ and therebycomputes the path metric value (Step S801).

Then, the control unit 140 of the information processing device 100extracts a record of which destination (Dest 341) is set to thetransmission source station of which the identifier is stored in theOrigSTA field 322 of the received PREQ from the mesh path table 350(Step S802). This record will also be referred to as a structurevariable TAB.

Next, the control unit 140 of the information processing device 100determines whether or not there is a record of which the destination isset to the transmission source station of which the identifier is storedin the OrigSTA field 322 (Step S803). When there is no such record (StepS803), the control unit 140 of the information processing device 100generates a new record of which the destination (Dest 341) is set to thetransmission source station in the mesh path table 350 (Step S804).

In addition, when there is a record of which the destination is set tothe transmission source station of which the identifier is stored in theOrigSTA field 322 (Step S803), the control unit 140 of the informationprocessing device 100 determines whether or not a path candidate is tobe set (Step S805). In other words, the control unit 140 of theinformation processing device 100 determines whether or not the value ofthe SeqNum field 324 of the received PREQ is greater than the value ofthe Cand. SeqNum 356 of the TAB (shown in FIG. 21). In addition, thecontrol unit 140 of the information processing device 100 determineswhether or not the values coincide and the computed path metric value(the path metric value from the transmission source station to theself-device) is smaller than the value of the Cand. Metric 355 of theTAB (shown in FIG. 21).

When these conditions for being a path candidate are satisfied (StepS805), the control unit 140 of the information processing device 100determines that the transmitting station of the PREQ received this timeis the path candidate to the destination station of the extracted record(Step S805). In this case, the control unit 140 of the informationprocessing device 100 stores the information in each of the record itemsthereof as shown in a of FIG. 23 (Step S806). This corresponds to aprocess in which path candidate information is temporarily retained(Step S806).

Specifically, the ProactiveFlag 351 of “e” of the Index 346 storesTrueValue or FalseValue based on the flags field 321 or the DestSTAfield 323 of the received PREQ. In other words, when the flags field 321indicates a proactive mesh path generation process, or broadcast isdesignated in the DestSTA field 323, TrueValue is stored. On the otherhand, FalseValue is stored in other cases.

In addition, in the Cand. Flag 353 of “g” of the Index 346, theindication that the information is valid is set. That is, TrueValue isstored.

In addition, in the Cand. NextHop 354 of “h” of the Index 346, theidentifier of the TX STA ADDR field 303 of the received PREQ is stored.

In addition, in the Cand. Metric 355 of “i” of the Index 346, thecomputed path metric value (the path metric value from the transmissionsource station to the self-device) is stored.

In addition, in the Cand. SeqNum 356 of “j” of the Index 346, the valuestored in the SeqNum field 324 of the received PREQ is stored.

In addition, in the Cand. ExpTime 357 of “k” of the Index 346, the valueobtained by adding the current time to the value stored in the Lifetimefield 327 of the received PREQ (the expiration time of the mesh path) isstored.

In addition, in the Cand. ActReason 358 of “n” of the Index 346, 2 isstored when the self-device is recorded in the DestSTA field 323 of thePREQ. In this case, the refreshing process is set to be triggered thesecond earliest. On the other hand, when the self-device is not recordedin the DestSTA field 323 of the PREQ, the value of the HopCount field325 of the PREQ×2+4 is stored.

On the other hand, when it is determined not to be the path candidate(Step S805), the control unit 140 of the information processing device100 discards the PREQ and finishes the operation of the PREQ receptionprocess.

Then, the control unit 140 of the information processing device 100determines whether or not the transmission source station of thereceived PREQ coincides with the transmitting station (Step S807). Inother words, the control unit 140 of the information processing device100 determines whether or not the identifier stored in the OrigSTA field322 of the PREQ coincides with the identifier stored in the TX STA ADDRfield 303 of the PREQ (Step S807). Here, when the transmission sourcestation of the received PREQ does not coincide with the transmittingstation, it means that the received PREQ has been transmitted fromanother information processing device (transmission source station).

In addition, when the transmission source station of the received PREQdoes not coincide with the transmitting station (Step S807), the controlunit 140 of the information processing device 100 extracts a record ofwhich the destination is set to the transmitting station from the meshpath table 350 (Step S808). In other words, the control unit 140 of theinformation processing device 100 extracts the record of which thedestination is set to the transmitting station of which the identifieris stored in the TX STA ADDR field 303 from the mesh path table 350(Step S808).

Then, the control unit 140 of the information processing device 100determines whether or not there is a record of which the destination isset to the transmitting station of which the identifier is stored in theTX STA ADDR field 303 (Step S809). When there is no such record (StepS809), the control unit 140 generates a new record of which thedestination (Dest 341) is set to the transmitting station in the meshpath table 350 (Step S810).

In addition, the case in which there is a record of which thedestination is set to the transmitting station of which the identifieris stored in the TX STA ADDR field 303 is assumed (Step S809). In thiscase, the control unit 140 of the information processing device 100stores the content of the received PREQ as a direct communicationstation candidate (nearby communication station candidate) (Step S811).In other words, the control unit 140 of the information processingdevice 100 stores the information in each of the record items thereof asshown in b of FIG. 23 (Step S811). This corresponds to a process inwhich the path candidate information is temporarily retained (StepS811).

Specifically, in the Cand. Flag 353 of “g” of the Index 346, the factthat the information is valid is stored. In other words, TrueValue isstored.

In addition, in the Cand. NB. Metric 359 of “p” of the Index 346, thelink metric value between the transmitting station of the received PREQand the self-station is stored.

In addition, in the Cand. NB. ExpTime 360 of “q” of the Index 346, thevalue obtained by adding the current time to the value stored in theLifetime field 327 of the received PREQ (the expiration time of the meshpath) is stored.

Then, the control unit 140 of the information processing device 100determines whether the destination station of the received PREQcoincides with the self-station (Step S812). In other words, the controlunit 140 of the information processing device 100 determines whether theidentifier stored in the DestSTA field 323 of the received PREQcoincides with the identifier of the self-device (Step S812).

Then, when the destination station of the received PREQ does notcoincide with the self-station (Step S812), the control unit 140 of theinformation processing device 100 performs a transfer process of thereceived PREQ (Step S813). In this case, the control unit 140 of theinformation processing device 100 updates the Metric field 326 of thereceived PREQ with the path metric value, and updates the HopCount field325 with an incremented value, and then the PREQ with the updated fieldsis transferred (Step S813).

When the destination station of the received PREQ coincides with theself-station (Step S812), the control unit 140 of the informationprocessing device 100 starts the response process with a PREP, withoutperforming the transfer process of the received PREQ (Step S814). Here,the control unit 140 of the information processing device 100 does notimmediately perform the reply with the PREP, but sets a timer forholding a grace period before the PREP is transmitted (Step S814). Itshould be noted that, when a timer for the reply process destined forthe transmission source station corresponding to the OrigSTA field 322of the received PREQ is already set, the process ends with no furtheroperation.

[Setting Example of a Timer]

Next, the timer set in the reply process with the PREQ will bedescribed.

As described above, when generating a path, an information processingdevice waits until a destination station replies with a PREP after thedevice transmits a PREQ. When there is no reply after a predeterminedperiod of time elapses from the transmission of the PREQ, theinformation processing device re-transmits the PREQ. Thus, if a value ofthe timer (a grace period until the transmission of a PREP) issignificantly exceeded, there is concern of wasteful re-transmission ofthe PREQ being induced due to a delay in transmission of a PREP.

A time taken until re-transmission of a PREQ is decided based on, forexample, a parameter value used in the system. The IEEE 802.11s standardstipulates, for example, the time taken until re-transmission of a PREQas equal to or longer than 2×(dot11MeshHWMPnetDiameteTraversalTime) atthe minimum. Here, (dot11MeshHWMPnetDiameterTraversalTime) is anestimated value necessary for the process from transmission of a pathrequest signal by an information processing device to spread of thesignal over a network through relay of the signal. For this reason, itis necessary to set a value of the timer (a grace period until thetransmission of a PREP) to a value smaller than the estimated value.

In addition, the IEEE 802.11s standard stipulates, for example, anestimated value which indicates the number of hops in relay necessaryfor a path request signal to spread over the network after theinformation processing device transmit the signal. Specifically, as theestimated value, a parameter (dot11MeshHWMPnetDiameter) is decided.Using these parameters, an estimated value A of a transfer time per hopcan be computed with the following expression.

A=(dot11MeshHWMPnetDiameterTraversalTime)+(dot11MeshHWMPnetDiameter)

In addition, the value of the timer (a grace period until thetransmission of a PREP) is preferably set to be greater than theestimated value A.

Taking the above points into consideration, the value of the timer (agrace period until the transmission of a PREP) B is preferably set tosatisfy the following condition.

B<(dot11MeshHWMPnetDiameterTraversalTime)×C

B>A×D

Here, C is a constant, and for example, a value from about 4 to 16 canbe set. In addition, D is a constant, and a value from about 1 to 8 canbe set.

As described above, the value of the timer (a grace period until thetransmission of a PREP) is useless if it is too short, but if it is toolong, destabilized behavior of the system is induced, and thus it isimportant to set a proper value.

As described above, the control unit 140 can decide the value of thetimer (predetermined time) based on the two estimated values(dot11MeshHWMPnetDiameterTraversalTime and dot11MeshHWMPnetDiameter)

[Reception Process and Transmission Process of a PREP]

When the timer for transmission of the PREP described above is over orwhen a PREP destined for an information processing device other than theself-station has been received, the information processing device 100starts a transmission process of a PREP. Thus, the process at the timeof transmission of the PREP will be described using FIGS. 25 to 28.

FIGS. 25 and 26 are diagrams showing an example of updating the meshpath table 350 retained by the information processing device 100according to the first embodiment of the present technology. Thisupdating will be described in detail with reference to FIG. 27.

FIGS. 27 and 28 are flowcharts showing an example of the procedure ofsignal processing performed by the information processing device 100according to the first embodiment of the present technology.

First, the control unit 140 of the information processing device 100determines whether the process of this time is to be started as a replyprocess to a PREQ destined for the self-station or to be startedaccording to reception of a PREP (Step S821). When the process is to bestarted as a reply process to the PREQ destined for the self-station(Step S821), the control unit 140 of the information processing device100 transcribes information from the PREQ or the like, and generates aPREP to be transmitted (Step S833). By generating the PREP to betransmitted in this manner, a transmission process is prepared (StepS833).

When the process is to be started according to reception of a PREP (StepS821), the control unit 140 of the information processing device 100extracts a record corresponding to the transmission source station ofthe received PREP from the mesh path table 350 (Step S822). In otherwords, the control unit 140 of the information processing device 100extracts a record of which the destination (Dest 341) is set to thetransmission source station of which the identifier is stored in theDestSTA field 333 of the received PREP from the mesh path table 350(Step S822).

Next, the control unit 140 of the information processing device 100determines whether or not there is a record of which the destination isset to the transmission source station of which the identifier is storedin the DestSTA field 333 (Step S823). When there is no such record (StepS823), the control unit 140 of the information processing device 100generates a new record of which the destination (Dest 341) is set to thetransmission source station in the mesh path table 350 (Step S824).

In addition, when there is the record of which the destination is set tothe transmission source station of which the identifier is stored in theDestSTA field 333 (Step S823), the control unit 140 of the informationprocessing device 100 updates the record as shown in a of FIG. 25 (StepS825). This is a process corresponding to setting a mesh path.

Specifically, in the NextHop 342 of “a” of the Index 346, the TX STAADDR field 303 of the PREP is stored. In addition, in the Metric 343 of“b” of the Index 346, the path metric value computed by adding the linkmetric value between the transmitting station and the self-station tothe Metric field of the PREP is stored. In addition, in the SeqNum 344of “c” of the Index 346, the value of SeqNum of the PREP is stored. Inaddition, in the ExpTime 345 of “d” of the Index 346, the value obtainedby adding the current time to Lifetime of the PREP is stored. Inaddition, in the ActReason 352 of “f” of the index 346, 1 is stored whenthe self-station is the OrigSTA field 332 of the PREP, and the value ofthe HopCount field 335 of the PREP×2+3 is stored in other cases. Bystoring 1 in the ActReason 352 of “f” of the Index 346, the refreshingprocess can be set to be triggered as early as possible. In addition,FalseValue is stored in the Cand. Flag 353 of “g” of the Index 346, andthe same value as that stored in the SeqNum 344 of “c” of the Index 346is stored in the Cand. SeqNum of “j” of the Index 346.

Then, the control unit 140 of the information processing device 100determines whether or not the transmission source station of thereceived PREP coincides with the transmitting station of the receivedPREP (Step S826). In other words, the control unit 140 of theinformation processing device 100 determines whether or not theidentifier of the DestSTA field 333 of the received PREP coincides withthe identifier of the TX STA ADDR field 303 of the received PREP (StepS826).

When the transmission source station of the received PREP does notcoincide with the transmitting station of the received PREP (Step S826),the control unit 140 of the information processing device 100 extracts arecord of which the destination station is set to the transmittingstation from the mesh path table 350 (Step S827). In other words, thecontrol unit 140 of the information processing device 100 extracts arecord of which the destination (Dest 341) is set to the transmittingstation of which the identifier is stored in the TX STA ADDR field 303of the received PREP from the mesh path table 350 (Step S827).

Next, the control unit 140 of the information processing device 100determines whether or not there is a record of which the destination isset to the transmitting station of which the identifier is stored in theTX STA ADDR field 303 (Step S828). When there is no such record (StepS828), the control unit 140 of the information processing device 100generates a new record of which the destination (Dest 341) is set to thetransmitting station in the mesh path table 350 (Step S829).

In addition, when there is the record of which the destination is set tothe transmitting station of which the identifier is stored in the TX STAADDR field 303 (Step S828), the control unit 140 of the informationprocessing device 100 updates the record as shown in b of FIG. 25 (StepS830). This corresponds to a process of cutting overhead in generationof a path because a mesh path record destined for NextHop is alsogenerated on that occasion.

Specifically, in the NextHop 342 of “a” of the Index 346, the TX STAADDR field 303 of the PREP is stored. In addition, in the Metric 343 of“b” of the Index 346, the link metric value between the self-station andthe transmitting station is stored. In addition, in the SeqNum 344 of“c” of the Index 346, an invalid value (for example, a value determinedto be “smaller” than any value) is stored. In addition, in the ExpTime345 of “d” of the Index 346, the value obtained by adding the currenttime to the value of the Lifetime field 337 of the PREP is stored. Inaddition, 0 is stored in the ActReason 352 of “f” of the Index 346. As 0is stored in the ActReason 352 of “f” of the Index 346 as described, therefreshing process can be set to be triggered as late as possible. Inaddition, FalseValue is stored in the Cand. Flag 353 of “g” of the Index346, and further the same value as that stored in the SeqNum 344 of “c”of the Index 346 is stored in the Cand. SeqNum of “j” of the Index 346.

Then, the control unit 140 of the information processing device 100determines whether or not the identifier stored in the OrigSTA field 322of the received PREP is of the self-station (Step S831). When theidentifier stored in the OrigSTA field 322 of the received PREP is ofthe self-station (Step S831), the operation of the reception process ofthe PREP ends.

When the identifier stored in the OrigSTA field 322 of the received PREPis not of the self-station (Step S831), the control unit 140 of theinformation processing device 100 generates a PREP (Step S832). In otherwords, the control unit 140 of the information processing device 100updates the value of the Metric field 336 of the received PREP by addingthe link metric value between the self-station and the transmittingstation thereto, updates the HopCount with an incremented value, andthereby generates a PREP (Step S832). In this manner, by generating thePREP to be transferred, the transmission process is prepared (StepS832).

Then, the control unit 140 of the information processing device 100updates the record which corresponds to the OrigSTA field 332 of theprepared PREP for transmission (Step S834). In other words, the controlunit 140 of the information processing device 100 extracts the recordwhich corresponds to the OrigSTA field 332 of the prepared PREP fortransmission from the mesh path table 350. Then, the control unit 140 ofthe information processing device 100 checks that the Cand. Flag 353 ofthe extracted record (“g” of the Index 346) has turned into TrueValue.Then, the control unit 140 of the information processing device 100updates this record as shown in a of FIG. 26 (Step S834). Thiscorresponds to a process in which information primarily retained whenthe PREQ was received (path candidate information) is reflected as shownin FIG. 24.

Specifically, in the NextHop 342 of “a” of the Index 346, the value ofthe Cand. NextHop 354 of the record is transcribed. In addition, in theMetric 343 of “b” of the Index 346, the value of the Cand. Metric 355 ofthe record is transcribed. In addition, in the SeqNum 344 of “c” of theIndex 346, the value of the Cand. SeqNum 356 of the record istranscribed. In addition, in the ExpTime 345 of “d” of the Index 346,the value of the Cand. ExpTime 357 of the record is transcribed. Inaddition, in the ActReason 352 of “f” of the Index 346, the value of theCand. ActReason 358 of the record is transcribed. In addition, in theCand. Flag 353 of “g” of the Index 346, the indication that theinformation is invalid is set (in other words, FalseValue is stored).

In addition, depending on cases, the ProactiveFlag 351 of the record isreferred to, and the record is transcribed into the ProactiveFlag 351 ofthe record extracted in Step S822. It should be noted that this processis necessary only when the proactive PREQ is used.

Then, the control unit 140 of the information processing device 100determines whether or not the OrigSTA field 332 of the received PREP(the destination station of the PREP) coincides with the NextHop of therecord updated in Step S834 (Step S835). When they do not coincide (StepS835), the control unit 140 of the information processing device 100updates a record of which the destination station is set to the NextHop(Step S836). In other words, the control unit 140 of the informationprocessing device 100 extracts the record of which the destinationstation is set to the NextHop from the mesh path table 350. Then, thecontrol unit 140 of the information processing device 100 checks whetherthe Cand. Flag 353 of the extracted record has turned into TrueValue.Then, the control unit 140 of the information processing device 100updates the record as shown in b of FIG. 26 (Step S836). Thiscorresponds to a process in which information (nearby path candidateinformation) primarily retained when the PREQ has been received isreflected as shown in FIG. 24, and to a process of cutting overhead ingeneration of a path as a mesh path record destined for the NextHop isgenerated.

Specifically, in the NextHop 342 of “a” of the Index 346, the NextHop ofthe record using the OrigSTA of the PREP as a key is stored. Inaddition, the value of the Cand. NB. Metric 359 of the record istranscribed into the Metric 343 of “b” of the Index 346. In addition, inthe SeqNum 344 of “c” of the Index 346, an invalid value (for example, avalue determined to be “smaller” than any value) is stored. In addition,the value of the Cand. NB. ExpTime of the record is transcribed into theExpTime 345 of “d” of the Index 346. In addition, 0 is stored in theActReason 352 of “f” of the Index 346. In other words, as 0 is stored inthe ActReason 352 of “f” of the Index 346 as described, (the refreshingprocess can be set to be triggered as late as possible. In addition,FalseValue is stored in the Cand. Flag 353 of “g” of the Index 346, andfurther, the same value as that stored in the SeqNum 344 of “c” of theIndex 346 is stored in the Cand. SeqNum of “j” of the Index 346.

Then, the control unit 140 of the information processing device 100transmits the PREP generated in Step S832 or S833 to the NextHopdestined for the OrigSTA of the PREP in unicast (Step S837). In the RXSTA ADDR field 302 of the PREP, the identifier (address) of the NextHopis stored.

[Adjustment Example of a Transmission Trigger of a PREQ]

FIG. 29 is a diagram showing a threshold value used when the informationprocessing device 100 according to the first embodiment of the presenttechnology adjusts a transmission trigger of a PREQ.

As described above, in order to investigate an information processingdevice to be set as a receiving station when data is to be transmittedto another information processing device, the information processingdevice 100 refers to the mesh path table 350. In other words, theinformation processing device 100 refers to the mesh path table 350 inorder to investigate an information processing device to be designatedas NextHop when data is to be transmitted to another informationprocessing device.

However, cases in which, as a result of referring to the mesh path table350, there is no record corresponding to the information processingdevice serving as a destination station, the record is not storing validinformation, or the expiration time of the record has passed areassumed. In those cases, the information processing device 100 generatesand transmits a PREQ for setting a valid mesh path to the destinationstation. In addition, when an RANN has been received, the informationprocessing device 100 generates and transmits a PREQ for proactivegeneration of a mesh path.

Furthermore, even when a valid mesh path is stored in the recordextracted from the mesh path table 350, if the expiration time of themesh path is approaching, it is important to prevent a delay of datatransfer caused by invalidation of the valid mesh path. Thus, when theexpiration time is determined to be approaching even when a valid meshpath is stored in an extracted record, the information processing device100 transmits a PREQ for the purpose of refreshing the mesh path.

For example, when a value until the expiration time of a mesh path isequal to or smaller than a threshold value X (msec), the informationprocessing device 100 triggering transmission of a PREQ for the purposeof refreshing can be considered. However, if a plurality of informationprocessing devices on a mesh path simultaneously transmit PREQs for thepurpose of refreshing, overhead of management information increases, andtherefore it is important to cut the overhead.

Thus, in the embodiment of the present technology, the threshold value Xof the time until expiration is adjusted according to a value set in theActReason 352 of “f” of the Index 346 of a record of a mesh path.Specifically, the adjustment is performed as shown in FIG. 29.

In other words, when the value set in the ActReason 352 is 0, thecontrol unit 140 of the information processing device 100 does notadjust the threshold value. In other words, X′=X is set.

In addition, when the value set in the ActReason 352 is 1, the controlunit 140 of the information processing device 100 computes X′=X+800(msec) and uses it as the threshold value of the time until expiration.

In addition, when the value set in the ActReason 352 is 2, the controlunit 140 of the information processing device 100 computes X′=X+400(msec) and uses it as the threshold value of the time until expiration.

In addition, when the value set in the ActReason 352 is equal to orgreater than 3, the control unit 140 of the information processingdevice 100 computes X′=min(X+(20×the value of the ActReason 352), 300)and uses it as the threshold value of the time until expiration. Here,min(A, B) is a function outputting the smaller one between input valuesA and B.

Through this adjustment, the OrigSTA field 322 of the PREQ is set totrigger transmission of the PREQ the earliest for the purpose ofrefreshing, and the DestSTA field 323 of the PREQ is set to triggertransmission of the PREQ next for the purpose of refreshing. Inaddition, a relay station is set to be triggered at different timings.Accordingly, the plurality of information processing devices on the meshpath can be controlled not to simultaneously transmit the PREQ for thepurpose of refreshing.

Furthermore, for a mesh path destined for the NextHop that is a subsetof the mesh path, transmission of a PREQ for the purpose of refreshingis set to be triggered as late as possible, which can cut overhead ofmanagement information necessary for maintaining the mesh paths.

In this manner, based on the position of the information processingdevice 100 on a mesh path (communication path), the control unit 140changes an effective time for specifying a time at which pathinformation thereof is destroyed.

[Process Example when an RANN is Received]

FIG. 30 is a diagram showing an example of updating of the mesh pathtable 350 retained by the information processing device 100 according tothe first embodiment of the present technology. The updating will bedescribed in detail with reference to FIG. 31.

FIG. 31 is a flowchart showing an example of the process procedure ofsignal processing by the information processing device 100 according tothe first embodiment of the present technology.

As described above, in order to generate a proactive mesh path with aroot station, when an information processing device receives an RANN,the device transmits a PREQ to the transmission source station of theRANN in response thereto. Thus, in FIG. 31, an example of the procedureof signal processing by the information processing device 100 which hasreceived the RANN will be shown.

The control unit 140 of the information processing device 100 which hasreceived the RANN computes the path metric value to the informationprocessing device (transmission source station) of which the identifieris stored in the OrigSTA field 314 of the received RANN (Step S841). Forexample, the control unit 140 of the information processing device 100computes the link metric value between the self-station and theinformation processing device that transmitted the received RANN (theinformation processing device of which the identifier (address) isstored in the TX STA ADDR field 303). Then, the control unit 140 of theinformation processing device 100 computes the path metric value byadding the computed link metric value to the value stored in the Metricfield 317 of the received RANN (Step S841).

Then, the control unit 140 of the information processing device 100extracts a record of which destination (Dest 341) is set to thetransmission source station of which the identifier is stored in theOrigSTA field 314 of the received RANN from the mesh path table 350(Step S842). This record will also be referred to as a structurevariable TAB.

Next, the control unit 140 of the information processing device 100determines whether or not there is a record of which the destination isset to the transmission source station of which the identifier is storedin the OrigSTA field 314 (Step S843). When there is no such record (StepS843), the control unit 140 of the information processing device 100generates a new record of which the destination (Dest 341) is set to thetransmission source station in the mesh path table 350 (Step S844).

In addition, when there is a record of which the destination is set tothe transmission source station of which the identifier is stored in theOrigSTA field 314 (Step S843), the control unit 140 of the informationprocessing device 100 determines whether or not a path candidate is tobe set (Step S845). In other words, the control unit 140 of theinformation processing device 100 determines whether or not the value ofthe SeqNum 315 of the received RANN is greater than the value of theCand. SeqNum 356 of the TAB (shown in FIG. 21). In addition, the controlunit 140 of the information processing device 100 determines whether ornot the values coincide and the computed path metric value (the pathmetric value from the transmission source station to the self-device) issmaller than the value of the Cand. Metric 355 of the TAB (shown in FIG.21).

When these conditions for being a path candidate are satisfied (StepS845), the control unit 140 of the information processing device 100determines that the transmitting station of the RANN received this timeis the path candidate to the destination station of the extracted record(Step S845). In this case, the control unit 140 of the informationprocessing device 100 stores the information in each of the record itemsthereof as shown in FIG. 30 (Step S846). This corresponds to a processin which path candidate information is temporarily retained (Step S846).

Specifically, in the ProactiveFlag 351 of “e” of the Index 346,TrueValue is stored (optional). In addition, in the Cand. Flag 353 of“g” of the Index 346, the indication that the information is valid isset. In other words, TrueValue is stored in the Cand. Flag 353 of “g” ofthe Index 346.

In addition, in the Cand. NextHop 354 of “h” of the Index 346, theidentifier (address) of the TX STA ADDR field 303 of the RANN is stored.Furthermore, in the Cand. Metric 355 of “i” of the Index 346, thecomputed path metric value (the path metric value from the transmissionsource station to the self-station) is stored. In addition, in the Cand.SeqNum 356 of “j” of the Index 346, the value of the SeqNum field 315 ofthe received RANN is stored.

On the other hand, when the station is determined not to be a pathcandidate (Step S845), the control unit 140 of the informationprocessing device 100 discards the RANN and finishes the operation ofthe reception process of the RANN.

In addition, when the station is determined to be a path candidate (StepS845) and the information is stored (Step S846), the control unit 140 ofthe information processing device 100 starts a generation process of aPREQ (Step S847). Here, the control unit 140 of the informationprocessing device 100 does not immediately perform the reply with thePREQ, but sets a timer for holding a grace period before the PREQ istransmitted (Step S847). It should be noted that, when a timer for ageneration process of a PREQ destined for the transmission sourcestation corresponding to the OrigSTA field 314 of the received RANN hasalready been set, the process ends without setting a timer. Then, thecontrol unit stands by until the timer is over.

Then, the control unit 140 of the information processing device 100performs a transfer process of the received RANN (Step S848). In thiscase, the control unit 140 of the information processing device 100updates the Metric field 317 of the received RANN with the path metricvalue, and updates the HopCount field 316 with an incremented value, andtransfers the RANN with the updated values (Step S848).

It should be noted that, although not illustrated in FIG. 31, when thetimer for the generation process of the PREQ is over, the transmissionprocess of the PREQ is started.

[Timer Setting Example]

Next, the timer set according to the reply process to the RANN will bedescribed.

Here, as described above, the value of the timer (a grace period untilthe transmission of the PREQ) is useless if it is too short, but if itis too long, a destabilized behavior of the system is induced, and thusit is important to set a proper value. In addition, as described above,the estimated value A of a transfer time per hop can be computed withthe following expression.

A=(dot11MeshHWMPnetDiameterTraversalTime)+(dot11MeshHWMPnetDiameter)

Thus, the grace period until the transmission of the PREP is preferablyset to be greater than the estimated value A.

In addition, the value of the timer (the grace period until thetransmission of the PREQ) B is preferably set to satisfy the followingcondition.

B>A×D

Here, D is a constant and can be set to a value from about 1 to 8.

As above, the control unit 140 controls a timing at which pathinformation regarding a mesh path (communication path) set throughexchanging of a signal is confirmed to be delayed with reference to areception timing of the signal. Specifically, after receiving a pathrequest signal (a PREQ or an RANN), the control unit 140 retains pathinformation regarding a communication path to the transmission sourcestation of the path request signal in the mesh path table 350 as pathcandidate information. Then, the control unit 140 confirms the pathcandidate information as the path information regarding thecommunication path to the transmission source station at the timing atwhich a path reply signal (a PREP or a PREQ) corresponding to the pathrequest signal is transmitted to the transmission source station.

In addition, after receiving a path request signal of which thedestination is not the information processing device 100, the controlunit 140 retains path information regarding a communication path to thetransmitting station which has transmitted the path request signal inthe mesh path table 350 as nearby path candidate information. Then, thecontrol unit 140 confirms the nearby path candidate information as thepath information regarding the communication path to the transmittingstation at the timing at which a path reply signal corresponding to thepath request signal is transmitted to the transmission source signal.

In addition, after receiving a path request signal of which thedestination is the information processing device 100, the control unit140 transmits a path reply signal corresponding to the path requestsignal to the transmission source station of the path request signal atthe timing at which a predetermined period of time (timer) elapses fromreception of the path request signal. It should be noted that, althoughthe example in which the Cand. SeqNum 356 (“j” of the Index 346) isprovided as an item of the mesh path table 350 has been shown in theembodiment of the present technology, the Cand. SeqNum 356 may beomitted. When the Cand. SeqNum 356 is omitted like that, for example,the storage process and the reading process with respect to the Cand.SeqNum 356 described above can be interpreted as a storage process and areading process with respect to the SeqNum 344.

2. Second Embodiment

The case in which, when an active mesh path is generated, a PREQ istransmitted in broadcast has been shown in the first embodiment of thepresent technology. When the PREQ is transmitted in broadcast, however,there is a possibility of the PREQ dissipating due to collision ofsignals or the like. When the PREQ dissipates in that way, for example,an improper mesh path may be set as shown in FIG. 20.

Therefore, in a second embodiment of the present technology, an examplein which, when an information processing device transmits managementinformation (a PREQ or an RANN) to a destination station between which avalue mesh path is being retained, the information processing deviceperforms unicast transmission along with broadcast transmission to aNextHop will be shown. It should be noted that a communication system ofthe second embodiment of the present technology is substantially thesame as the communication system 200 shown in FIG. 1 and the like. Thus,the same reference symbols are given to the common parts with thecommunication system 200, and part of description thereof will beomitted.

[Example of Updating of a Valid Mesh Path]

FIGS. 32 and 33 are diagrams showing examples of transmission of a PREQby each of the information processing devices which constitute thecommunication system 200 according to the second embodiment of thepresent technology.

In FIGS. 32 and 33, a case in which there is a valid mesh path betweenthe information processing device 100 and the information processingdevice 220 passing through the information processing device 210 isassumed. An example in which the information processing device 100transmits a PREQ destined for the information processing device 220 forthe purpose of refreshing the mesh path in that case is shown.

In a of FIG. 32, an example in which the information processing device100 transmits a PREQ destined for the information processing device 220in unicast is shown. In b of FIG. 32, an example in which theinformation processing device 100 transmits PREQs destined for theinformation processing device 220 in broadcast is shown.

In a of FIG. 33, an example in which a PREQ from the informationprocessing device 100 destined for the information processing device 220is transmitted in unicast is shown. In b of FIG. 33, an example in whichPREQs from the information processing device 100 destined for theinformation processing device 220 are transmitted in broadcast is shown.

As shown in a of FIG. 32, the information processing device 100transmits the PREQ to the information processing device 210 in unicastfor the purpose of refreshing the mesh path. In other words, theinformation processing device 100 transmits the PREQ in which theinformation processing device 220 is designated in the DestSTA field 323to the information processing device 210 designated in the NextHop 342destined for the information processing device 220 in unicast.

In addition, as shown in b of FIG. 32, the information processing device100 transmits in broadcast the PREQs having the same content as the PREQtransmitted in unicast.

As shown in a and b of FIG. 32, when the PREQs having the same contentare transmitted in unicast and broadcast, the information processingdevice 210 overlappingly receives two PREQs having the same content.When two PREQs having the same content are overlappingly received inthis way, one of the PREQs is destroyed in the above-described receptionprocedure. Thus, overlapping transmission of two PREQs having the samecontent is not a problem.

Here, when a signal transmitted in unicast collides with another signal,a re-transmission process is performed using ARQ. Thus, even when a PREQtransmitted in unicast collides with another signal, a re-transmissionprocess of a PREQ is performed, and thus a PREQ can be delivered to theinformation processing device 210 with high reliability.

Upon receiving the PREQ, the information processing device 210 processesthe received PREQ in the above-described procedure, updates the recordsof the internal mesh path table 350, and starts a transfer process ofthe received PREQ.

Here, as shown in a of FIG. 33, upon recognizing that there is a validmesh path destined for the DestSTA of the PREQ, the informationprocessing device 210 also transmits the PREQ destined for the NextHopin unicast. In addition, the information processing device 210 transmitsin broadcast a PREQ having the same content as the PREQ transmitted inunicast as shown in b of FIG. 33.

By receiving the PREQ transmitted from the information processing device210, the information processing device 220 starts a reply process with aPREP. Accordingly, a finally stabilized mesh path between theinformation processing device 100 and the information processing device220 can be maintained.

An operation example of updating a valid mesh path will be described indetail with reference to FIG. 34.

[Operation Example of Updating of a Valid Mesh Path]

FIG. 34 is a flowchart showing the procedure of signal processing by theinformation processing device 100 according to the second embodiment ofthe present technology.

When a transmission process of a PREQ is started, the control unit 140of the information processing device 100 extracts the mesh path table350 corresponding to the destination station of the PREQ and determineswhether or not there is a valid mesh path to the destination station(Step S851). When there is a valid mesh path to the destination station(Step S851), the control unit 140 of the information processing device100 transmits the PREQ in unicast to the NextHop 342 of the valid meshpath (Step S852).

Then, the control unit 140 of the information processing device 100transmits in broadcast the same PREQ as the PREQ transmitted in unicast(Step 8853).

It should be noted that, although the example in which the PREQ istransmitted in unicast and then the PREQ is transmitted in broadcast hasbeen shown in FIG. 34, the PREQ may be transmitted in broadcast and thenthe PREQ may be transmitted in unicast.

[Operation Example of RANN Transmission]

As described above, vulnerability of a PREQ to collision with a signaltransmitted in broadcast when a valid mesh path is updated can be saidto be shared by an RANN used when a mesh path is proactively generated.In other words, there is a possibility of an RANN dissipating due tocollision or the like since it also is transmitted in broadcast, andthus there is a possibility of a mesh path which is unstable due to suchdissipation being generated.

Thus, in the second embodiment of the present technology, an informationprocessing device which transmits an RANN is also designed to performunicast transmission to an information processing device correspondingto the NextHop of a valid mesh path. An operation example of theinformation processing device in this case is shown in FIG. 35.

FIG. 35 is a flowchart showing the procedure of signal processing by theinformation processing device 100 according to the second embodiment ofthe present technology.

When a transmission process of an RANN is started, the control unit 140of the information processing device 100 scans each record of the meshpath table 350 and repeatedly performs a process of extracting aproactively generated mesh path (Loop L860). Here, whether or not it isa proactively generated mesh path can be determined by referring to theProactiveFlag 351 of the record.

Then, when there is a record of a proactively generated mesh path, thecontrol unit 140 of the information processing device 100 extracts theNextHop 342 of the record (Step S861). Then, the control unit 140 of theinformation processing device 100 determines whether or not the RANN tobe transmitted this time has already been transmitted to the NextHop 342in unicast (Step S862).

Then, when the signal has not been transmitted in unicast (Step S862),the control unit 140 of the information processing device 100 transmitsthe RANN to the NextHop 342 in unicast (Step S863). However, when theRANN signal is triggered by receiving an RANN from another informationprocessing device, the RANN is not transmitted to the transmittingstation of the received RANN.

Then, the control unit 140 of the information processing device 100records in the NextHop 342 the fact that the RANN has been transmittedin unicast (Step S864). For example, the control unit 140 of theinformation processing device 100 records the identifier of the NextHop342 to which the RANN has been transmitted in unicast and the fact thatthe RANN has been transmitted in unicast in the memory 150 (Step S864).

When this recording process has ended (Step S864), or the signal isdetermined to have been transmitted in unicast (Step S862), the processof extracting a proactively generated mesh path is repeatedly performed(Loop L860).

In addition, when the scanning ends (Loop L860), the control unit 140 ofthe information processing device 100 transmits the RANN in broadcast(Step S865). Accordingly, the RANN signal can be transmitted as stablyas necessary.

Although the example in which the RANN is transmitted in unicast andthen the RANN is transmitted in broadcast has been shown in FIG. 35, theRANN may be transmitted in broadcast and then the RANN may betransmitted in unicast.

Here, a case in which the information processing device 100 transmits anRANN to all information processing devices near the informationprocessing device 100 (nearby stations) in unicast can also be assumed.In such a case, the information processing device 100 can skip broadcasttransmission.

[Transmission Example of a Proactive PREQ]

As a technique for proactively generating a mesh path, a method in whicha root station regularly transmits a proactive PREQ is also considered,in addition to the method using an RANN.

The proactive PREQ is a PREQ signal which is transmitted with abroadcast address described in the DestSTA field 323 and eachinformation processing device which receives the signal is designated asa destination station. Similar to an RANN, the proactive PREQ is alsoregularly transmitted from a root station. Since this proactive PREQ isalso transmitted in broadcast, there is a possibility of the signaldissipating due to collision or the like, and there is a possibility ofa mesh path which is unstable due to such dissipation being generated.

Thus, in the second embodiment of the present technology, an informationprocessing device which transmits a proactive PREQ performs unicasttransmission to an information processing device corresponding to theNextHop of a valid mesh path. An operation example of an informationprocessing device in that case is shown in FIG. 36.

FIG. 36 is a flowchart showing the procedure of signal processing by theinformation processing device 100 according to the second embodiment ofthe present technology.

When a transmission process of a proactive PREQ is started, the controlunit 140 of the information processing device 100 scans each record ofthe mesh path table 350 and repeatedly performs a process of extractinga proactively generated mesh path (Loop L870). Here, whether or not itis a proactively generated mesh path can be determined by referring tothe ProactiveFlag 351 of the record.

Then, when there is a record of a proactively generated mesh path, thecontrol unit 140 of the information processing device 100 extracts theNextHop 342 of the record (Step S871). Then, the control unit 140 of theinformation processing device 100 determines whether or not theproactive PREQ to be transmitted this time has already been transmittedto the NextHop 342 in unicast (Step S872).

Then, when the signal is not transmitted in unicast (Step S872), thecontrol unit 140 of the information processing device 100 transmits theproactive PREQ to the NextHop 342 in unicast (Step S873). However, whenthe transmission of the PREQ is triggered by receiving a PREQ fromanother information processing device, the PREQ is not transmitted inunicast to the transmitting station of the received PREQ.

Then, the control unit 140 of the information processing device 100records in the NextHop 342 the fact that the proactive PREQ has beentransmitted in unicast (Step S874). For example, the control unit 140 ofthe information processing device 100 records the identifier of theNextHop 342 to which the proactive PREQ has been transmitted in unicastand the fact that the proactive PREQ has been transmitted in unicast inthe memory 150 (Step S874).

When this recording process has ended (Step S874), or the signal isdetermined to have been transmitted in unicast (Step S872), the processof extracting a proactively generated mesh path is repeatedly performed(Loop L870).

In addition, when the scanning ends (Loop L870), the control unit 140 ofthe information processing device 100 transmits the proactive PREQ inbroadcast (Step S875). Accordingly, the proactive PREQ signal can betransmitted as stably as necessary.

Although the example in which the proactive PREQ is transmitted inunicast and then the proactive PREQ is transmitted in broadcast has beenshown in FIG. 36, the proactive PREQ may be transmitted in broadcast andthen the proactive PREQ may be transmitted in unicast.

Here, a case in which the information processing device 100 transmits aproactive PREQ to all information processing devices near theinformation processing device 100 (nearby stations) in unicast can alsobe assumed. In such a case, the information processing device 100 canskip broadcast transmission.

As described above, when a signal is transmitted to another informationprocessing device and there is path information regarding acommunication path to the other information processing device, thecontrol unit 140 transmits the signal to the other informationprocessing device in unicast, and performs control to transmit thesignal in broadcast. In addition, when there is no path informationregarding the communication path to the information processing device,the control unit 140 transmits the signal in broadcast.

In addition, when a signal for updating a proactively generatedcommunication path is transmitted, the control unit 140 transmits thesignal in unicast to an information processing device that is the nextdestination specified by path information regarding the communicationpath and transmits the signal in broadcast.

As described above, according to the embodiment of the presenttechnology, a stable multi-hop path can be provided in the mesh pathgeneration process. In addition, in the mesh path updating process, astable multi-hop path can be provided while unnecessary overhead is cut.That is, stability of a mesh path can be enhanced. In other words,generation and management of a communication path between a plurality ofinformation processing devices can be properly performed.

3. Application Example

The technology of the present disclosure can be applied to variousproducts. For example, the information processing device 100 may berealized as a mobile terminal such as a smartphone, a tablet-typepersonal computer (PC), a notebook PC, a portable game terminal, or adigital camera, a fixed-type terminal such as a television receiver set,a printer, a digital scanner, or a network storage, or an in-vehicleterminal such as a car navigation device. In addition, the informationprocessing device 100 may be realized as a terminal which performsmachine-to-machine (M2M) communication (which is also referred to as amachine-type communication (MTC) terminal) such as a smart meter, avending machine, a remote monitoring device, or a point-of-sale (POS)terminal. Furthermore, the information processing device 100 may be awireless communication module (for example, an integrated circuit moduleconfigured in one die) mounted in these terminals.

3-1. First Application Example

FIG. 37 is a block diagram showing an example of a schematicconfiguration of a smartphone 900 to which the technology of the presentdisclosure may be applied. The smartphone 900 includes a processor 901,a memory 902, a storage 903, an external connection interface 904, acamera 906, a sensor 907, a microphone 908, an input device 909, adisplay device 910, a speaker 911, a wireless communication interface913, an antenna switch 914, an antenna 915, a bus 917, a battery 918,and an auxiliary controller 919.

The processor 901 may be, for example, a central processing unit (CPU)or a system on a chip (SoC), and controls functions of an applicationlayer and another layer of the smartphone 900. The memory 902 includes arandom access memory (RAM) and a read only memory (ROM), and stores aprogram that is executed by the processor 901, and data. The storage 903may include a storage medium such as a semiconductor memory or a harddisk. The external connection interface 904 is an interface forconnecting an external device such as a memory card or a universalserial bus (USB) device to the smartphone 900.

The camera 906 includes an image sensor such as a charge coupled device(CCD) and a complementary metal oxide semiconductor (CMOS), andgenerates a captured image. The sensor 907 may include a group ofsensors such as a measurement sensor, a gym sensor, a geomagneticsensor, and an acceleration sensor. The microphone 908 converts soundsthat are input to the smartphone 900 to audio signals. The input device909 includes, for example, a touch sensor configured to detect touchonto a screen of the display device 910, a keypad, a keyboard, a button,or a switch, and receives an operation or an information input from auser. The display device 910 includes a screen such as a liquid crystaldisplay (LCD) and an organic light-emitting diode (OLED) display, anddisplays an output image of the smartphone 900. The speaker 911 convertsaudio signals that are output from the smartphone 900 to sounds.

The wireless communication interface 913 supports one or more ofwireless LAN standards such as IEEE 802.11a, 11b, 11g, 11n, 11ac, and11ad to execute wireless communication. The wireless communicationinterface 913 can communicate with another device via a wireless LANaccess point in an infrastructure mode. In addition, the wirelesscommunication interface 913 can directly communicate with another devicein an ad hoc mode. The wireless communication interface 913 cantypically include a baseband processor, a radio frequency (RF) circuit,and a power amplifier. The wireless communication interface 913 may be aone-chip module in which a memory which stores a communication controlprogram, a processor which executes the program and a relevant circuitare integrated. The wireless communication interface 913 may supportother kinds of wireless communication schemes such as a near fieldwireless communication scheme, a proximity wireless communication schemeor a cellular communication scheme in addition to the wireless LANscheme. The antenna switch 914 switches connection destinations of theantenna 915 between a plurality of circuits (for example, circuits fordifferent wireless communication schemes) included in the wirelesscommunication interface 913. The antenna 915 has a single or a pluralityof antenna elements (for example, a plurality of antenna elements whichconstitute a MIMO antenna), which are used by the wireless communicationinterface 913 for transmission and reception of radio signals.

It should be noted that the smartphone 900 is not limited to the exampleof FIG. 37 and may include a plurality of antennas (for example, anantenna for a wireless LAN, an antenna for the proximity wirelesscommunication scheme, etc.). In that case, the antenna switch 914 may beomitted from the configuration of the smartphone 900.

The bus 917 connects the processor 901, the memory 902, the storage 903,the external connection interface 904, the camera 906, the sensor 907,the microphone 908, the input device 909, the display device 910, thespeaker 911, the wireless communication interface 913, and the auxiliarycontroller 919 to each other. The battery 918 supplies power to blocksof the smartphone 900 illustrated in FIG. 37 via feeder lines, which arepartially shown as dashed lines in the figure. The auxiliary controller919 operates a minimum necessary function of the smartphone 900, forexample, in a sleep mode.

In the smartphone 900 shown in FIG. 37, the communication unit 120, thecontrol unit 140, and the memory 150 described using FIG. 2 may beimplemented by the wireless communication interface 913. In addition, atleast some of these functions may be implemented by the processor 901 orthe auxiliary controller 919.

3-2. Second Application Example

FIG. 38 is a block diagram illustrating an example of a schematicconfiguration of a car navigation device 920 to which the technology ofthe present disclosure may be applied. The car navigation device 920includes a processor 921, a memory 922, a global positioning system(OPS) module 924, a sensor 925, a data interface 926, a content player927, a storage medium interface 928, an input device 929, a displaydevice 930, a speaker 931, a wireless communication interface 933, anantenna switch 934, an antenna 935, and a battery 938.

The processor 921 may be, for example, a CPU or a SoC, and controls anavigation function and another function of the car navigation device920. The memory 922 includes RAM and ROM, and stores a program that isexecuted by the processor 921, and data.

The OPS module 924 uses GPS signals received from a GPS satellite tomeasure a position (such as latitude, longitude, and altitude) of thecar navigation device 920. The sensor 925 may include a group of sensorssuch as a gyro sensor, a geomagnetic sensor, and an air pressure sensor.The data interface 926 is connected to, for example, an in-vehiclenetwork 941 via a terminal that is not shown, and acquires datagenerated by the vehicle, such as vehicle speed data.

The content player 927 reproduces content stored in a storage medium(such as a CD and a DVD) that is inserted into the storage mediuminterface 928. The input device 929 includes, for example, a touchsensor configured to detect touch onto a screen of the display device930, a button, or a switch, and receives an operation or an informationinput from a user. The display device 930 includes a screen such as aLCD or an OLED display, and displays an image of the navigation functionor content that is reproduced. The speaker 931 outputs sounds of thenavigation function or the content that is reproduced.

The wireless communication interface 933 supports one or more ofwireless LAN standards such as IEEE 802.11a, 11b, 11g, 11n, 11ac, and11ad to execute wireless communication. The wireless communicationinterface 933 can communicate with another device via a wireless LANaccess point in an infrastructure mode. In addition, the wirelesscommunication interface 933 can directly communicate with another devicein an ad hoc mode. The wireless communication interface 933 cantypically include a baseband processor, an RF circuit, and a poweramplifier. The wireless communication interface 933 may be a one-chipmodule in which a memory which stores a communication control program, aprocessor which executes the program and a relevant circuit areintegrated. The wireless communication interface 933 may support otherkinds of wireless communication schemes such as a near field wirelesscommunication scheme, a proximity wireless communication scheme or acellular communication scheme in addition to the wireless LAN scheme.The antenna switch 934 switches connection destinations of the antenna935 between a plurality of circuits included in the wirelesscommunication interface 933. The antenna 935 has a single or a pluralityof antenna elements, which are used by the wireless communicationinterface 933 for transmission and reception of radio signals.

In addition, the car navigation device 920 may include a plurality ofantennas, not limited to the example of FIG. 38. In that case, theantenna switches 934 may be omitted from the configuration of the carnavigation device 920.

The battery 938 supplies power to blocks of the car navigation device920 illustrated in FIG. 38 via feeder lines that are partially shown asdashed lines in the figure. The battery 938 accumulates power suppliedform the vehicle.

In the car navigation device 920 illustrated in FIG. 38, thecommunication unit 120, the control unit 140, and the memory 150described by using FIG. 2 may be implemented by the wirelesscommunication interface 933. At least a part of the functions may alsobe implemented by the processor 921.

The technology of the present disclosure may also be realized as anin-vehicle system (or a vehicle) 940 including one or more blocks of thecar navigation device 920, the in-vehicle network 941, and a vehiclemodule 942. The vehicle module 942 generates vehicle data such asvehicle speed, engine speed, and trouble information, and outputs thegenerated data to the in-vehicle network 941.

The above-described embodiments are examples for embodying the presenttechnology, and matters in the embodiments each have a correspondingrelationship with disclosure-specific matters in the claims. Likewise,the matters in the embodiments and the disclosure-specific matters inthe claims denoted by the same names have a corresponding relationshipwith each other. However, the present technology is not limited to theembodiments, and various modifications of the embodiments may beembodied in the scope of the present technology without departing fromthe spirit of the present technology.

The processing sequences that are described in the embodiments describedabove may be handled as a method having a series of sequences or may behandled as a program for causing a computer to execute the series ofsequences and recording medium storing the program. As the recordingmedium, a hard disk, a CD (Compact Disc), an MD (MiniDisc), and a DVD(Digital Versatile Disc), a memory card, and a Blu-ray disc (registeredtrademark) can be used.

Effects described in the present description are just examples, theeffects are not limited, and there may be other effects.

Additionally, the present technology may also be configured as below.

(1)

An information processing device including:

a communication unit configured to perform exchange of a signal forgeneration or updating of a multi-hop communication path using wirelesscommunication with another information processing device; and

a control unit configured to perform control in a manner that, whenthere is path information regarding a communication path to anotherinformation processing device in a case in which the signal istransmitted to the other information processing device, the signal istransmitted to the other information processing device in unicast, andthe signal is transmitted in broadcast.

(2)

The information processing device according to (1), wherein the controlunit transmits the signal in broadcast when there is no path informationregarding the communication path to the other information processingdevice.

(3)

The information processing device according to (1), wherein, when acommunication path which has been proactively generated is set and asignal for updating the communication path is transmitted, the controlunit transmits the signal in unicast to an information processing deviceserving as a next destination specified with path information regardingthe communication path and transmits the signal in broadcast.

(4)

The information processing device according to any of (1) to (3),wherein, when a path request signal of which a destination is theinformation processing device has been received as the signal, thecontrol unit causes a path reply signal corresponding to the pathrequest signal to be transmitted in the unicast and the broadcast to atransmission source station which is an information processing devicewhich has transmitted the path request signal first at a timing at whicha predetermined period of time elapses from reception of the pathrequest signal.

(5)

An information processing method including:

a communication procedure of performing exchange of a signal forgeneration or updating of a multi-hop communication path using wirelesscommunication with another information processing device; and

a control procedure of performing control in a manner that, when thereis path information regarding a communication path to anotherinformation processing device in a case in which the signal istransmitted to the other information processing device, the signal istransmitted to the other information processing device in unicast, andthe signal is transmitted in broadcast.

REFERENCE SIGNS LIST

-   100, 210, 220, 230, 240 information processing device-   110 antenna-   120 communication unit-   130 I/O interface-   140 control unit-   150 memory-   160 bus-   171 movement detection unit-   172 operation reception unit-   173 display unit-   174 audio output unit-   200 communication system-   900 smartphone-   901 processor-   902 memory-   903 storage-   904 external connection interface-   906 camera-   907 sensor-   908 microphone-   909 input device-   910 display device-   911 speaker-   913 wireless communication interface-   914 antenna switch-   915 antenna-   917 bus-   918 battery-   919 auxiliary controller-   920 car navigation device-   921 processor-   922 memory-   924 GPS module-   925 sensor-   926 data interface-   927 content player-   928 storage medium interface-   929 input device-   930 display device-   931 speaker-   933 wireless communication interface-   934 antenna switch-   935 antenna-   938 battery-   941 in-vehicle network-   942 vehicle module

1. An information processing device comprising: a communication unitconfigured to perform exchange of a signal for generation or updating ofa multi-hop communication path using wireless communication with anotherinformation processing device; and a control unit configured to performcontrol in a manner that when there is path information regarding acommunication path to another information processing device in a case inwhich the signal is transmitted to the other information processingdevice, the signal is transmitted to the other information processingdevice in unicast, and the signal is transmitted in broadcast.
 2. Theinformation processing device according to claim 1, wherein the controlunit transmits the signal in broadcast when there is no path informationregarding the communication path to the other information processingdevice.
 3. The information processing device according to claim 1,wherein, when a communication path which has been proactively generatedis set and a signal for updating the communication path is transmitted,the control unit transmits the signal in unicast to an informationprocessing device serving as a next destination specified with pathinformation regarding the communication path and transmits the signal inbroadcast.
 4. The information processing device according to claim 1,wherein, when a path request signal of which a destination is theinformation processing device has been received as the signal, thecontrol unit causes a path reply signal corresponding to the pathrequest signal to be transmitted in the unicast and the broadcast to atransmission source station which is an information processing devicewhich has transmitted the path request signal first at a timing at whicha predetermined period of time elapses from reception of the pathrequest signal.
 5. An information processing method comprising: acommunication procedure of performing exchange of a signal forgeneration or updating of a multi-hop communication path using wirelesscommunication with another information processing device; and a controlprocedure of performing control in a manner that, when there is pathinformation regarding a communication path to another informationprocessing device in a case in which the signal is transmitted to theother information processing device, the signal is transmitted to theother information processing device in unicast, and the signal istransmitted in broadcast.